Extended Incident Handling Working Group Kathleen M. Moriarty draft-ietf-inch-rid-01.txt MIT Lincoln Laboratory Expires: April 21, 2005 October 21, 2004 Incident Handling: Real-Time Inter-Network Defense Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract Network security incidents such as Denial of Service (DoS), system compromises, worms, and viruses typically result in the loss of service, data, and resources both human and system. Security incidents can be detrimental to the health of the network as a whole. Network Providers (NP) need to be equipped and ready to assist in tracing security incidents with tools and procedures in place before the occurrence of an attack. This paper proposes a proactive inter-network communication method to integrate existing tracing mechanisms across NP boundaries to identify the source(s) of an attack. The various methods implemented to detect and trace attacks must be coordinated on the NPs network as well as provide a communication mechanism across network borders. It is imperative that NPs have quick communication methods defined to enable neighboring NPs to assist in tracking a security incident across the Internet. This proposal integrates current incident detection and tracing practices for network traffic, which could be extended for security incident handling. Policy guidelines for handling incidents are recommended and can be agreed upon by a consortium using the defined protocol and extended to each NP's clients. Internet-Draft October 21, 2004 Moriarty Expires: April 21, 2005 [Page 2] Internet-Draft October 21, 2004 TABLE OF CONTENTS Status of this Memo ................................................ 1 Abstract ........................................................... 1 1. Introduction .................................................... 4 1.1 Overview of Attack Types ................................... 5 2. Recommended Network Provider (NP) Technologies .................. 7 3. Characteristics of Attacks ...................................... 8 3.1 Tracing a Distributed attack ............................... 9 3.1.1 Tracing Security Incidents ........................... 10 3.2 Trace Approaches ........................................... 11 3.2.1 Trace approach via Traffic Flow Analysis ............. 11 3.2.2 Trace Approach via Hash-Based IP Traceback ........... 12 3.2.3 IP Marking ........................................... 13 4. Communication Between Network Providers ......................... 14 4.1 Inter-Network Provider RID Messaging ....................... 15 4.2 RID Network Topology ....................................... 17 4.3 Message Formats ............................................ 18 4.3.1 RID Messages and Transport ........................... 19 4.3.2 RID Data Types ....................................... 19 4.3.4 IODEF-Document ...................................... 20 4.3.5 IODEF-Document Extensions ............................ 20 4.3.5.2 NPPath Extension ............................... 24 4.3.5.3 TraceStatus Extension ......................... 25 4.3.5.4 RIDPolicy Extension ........................... 26 4.4 RID Documents Defined by Message Type Derived from IODEF ... 28 4.4.1 Trace Request ........................................ 31 4.4.2 Trace Authorization Message .......................... 32 4.4.3 Source Found Message ................................. 33 4.4.4 Relay Message Request ................................ 34 4.4.5 Example Upstream Trace ............................... 36 4.4.6 RID Trace Request Example ............................ 37 5. RID IODEF Extension Document Type Definition .................... 40 5.1 RID Schema Definition with IODEF Schema Imported ........... 43 6. Message Transport ............................................... 46 6.1 Message Delivery Protocol - Integrity and Authentication ... 46 6.2 Transport Communication .................................... 47 6.3 Authentication of RID Protocol ............................. 47 6.4 Authentication Considerations for a Multi-hop Trace Request 48 6.4.1 Public Key Infrastructures and Consortiums ........... 49 6.5 Privacy Concerns and System Use Guidelines ................. 50 6.7 SOAP Wrapper ............................................... 54 Moriarty Expires: April 21, 2005 [Page 2] Internet-Draft October 21, 2004 7. Security Considerations ......................................... 55 8. Summary ......................................................... 57 9. References ...................................................... 59 9.1 Acknowledgements ........................................... 62 9.2 Author Information ......................................... 62 Moriarty Expires: April 21, 2005 [Page 3] Internet-Draft October 21, 2004 1. Introduction Incident handling involves the identification of the source of an attack, whether it be a system compromise or a denial of service attack. In order to identify the source of an attack, there must be a way to trace the attack traffic iteratively upstream through the network to the source. In cases where accurate records of an active session between the victim system and the attacker or source system are available, the source is easy to identify. The problem of tracing incidents becomes more difficult when the source is obscured or spoofed, logs are deleted, and the numbers of sources is overwhelming. Current approaches to mitigating the effects of security incidents, are aimed at identifying and filtering or rate limiting packets from attackers who seek to hide the origin of their attack by source address spoofing from multiple locations. Measures can be taken at network provider (NP) edge routers providing ingress, egress, and broadcast filtering as a recommended best practice in RFC2827. Network providers have devised solutions, in-house or commercial, to trace attacks across their backbone infrastructure to either identify the source on their network or the next upstream network in the path to the source. Techniques, such as collecting packets as traffic traverses the network, have been implemented to provide the capability to trace attack traffic after an incident has occurred. Other methods use packet marking techniques or flow based traffic analysis to trace traffic across the network in real time. The single network trace mechanisms use similar information across the individual networks to trace traffic. Problems may arise when an attempt is made to have a trace continued through the next upstream network since the trace mechanism and management may vary. In the case where the traffic traverses multiple networks, there is currently no established communication mechanism for continuing the trace. If the next upstream network has been identified, a phone call might be placed to contact the network administrators in an attempt to have them continue the trace. A communication mechanism is needed to facilitate the transfer of information to continue traces accurately and efficiently to upstream networks. The communication mechanism described in this paper, Real-time Inter- network Defense (RID), takes into consideration the information needed by various single network trace implementations and the requirement for network providers to decide if a Trace Request should be permitted to continue. The data in RID messages will be represented in an Extensible Markup Language (XML) document and is an extension of the Incident Data Exchange Format (IODEF) model. By following this model, integration with other aspects of the network for incident handling is simplified. Finally, methods are incorporated into the communication system to indicate what actions Moriarty Expires: April 21, 2005 [Page 5] Internet-Draft October 21, 2004 need to be taken closest to the source in order to cease or mitigate the effects of the attack at hand. RID is intended to provide a method to communicate the relevant information between NPs while being compatible with a variety of existing and possible future detection tracing, and response approaches. Security and privacy considerations are of high concern since potentially sensitive information may be passed through RID messages. RID messaging will take advantage of XML security, security and privacy policy information set in the RID extensions to IODEF, and will wrap RID messages in SOAP to use the authentication, integrity, and authorization features each has to offer to achieve the level of security that is necessary. SOAP is used as a message wrapper to direct messages appropriately and the SOAP binding will be used with a specific transport protocol that may include HTTPS, BEEP, S/MIME, XML SNMP, and others. 1.1 Overview of Attack Types RID messaging is intended for use in coordinating incident handling to locate the source of an attack and stop or mitigate the effects of the attack. The attack types include system or network compromises, denial of service attacks, or other malicious network traffic. RID is essentially a messaging system coordinating attack detection, tracing mechanisms, and the incident handling responses to locate the source of traffic. If a source address is spoofed, a more detailed trace of a packet (RID Trace Request) would be required to locate the true source. If the source address is valid, the incident handling may only involve the use of routing information to determine what network provider is closest to the source (RID Relay Request) and can assist with the remediation. The type of RID message used to locate a source is determined by the validity of the source address. RID message types are discussed in section 4.3. The CERT Coordination Center published a paper in October, 2001 entitled, "Trends in Denial of Service Attack Technology"[19]. The paper outlined the behavior of Denial of Service attacks of both single-source and multiple-source origins. Denial of Service (DoS) attacks attempt to consume bandwidth, processing power, or system resources for the purposes of denying use by normal users. Bandwidth or processing power based attacks may use variations on these packets, such as altering the source address, port numbers, or TCP options. DoS attacks are characterized by large amounts of traffic destined for particular Internet locations and can originate from a single or multiple sources. An attack from multiple sources is known as a Distributed Denial of Service attack (DDoS). Because DDoS attacks can originate from multiple sources, tracing such an attack can be extremely difficult or nearly impossible. Many Trace Requests may be required to accomplish the task and may require the use of Moriarty Expires: April 21, 2005 [Page 6] Internet-Draft October 21, 2004 dedicated network resources to communicate incident handling information to prevent a DoS against the RID system and network used for tracing and remediation. Provisions are suggested to reduce the load and prevent the same trace from occurring twice on a single network backbone in section 4 on communication between NPs. The attacks can be launched from systems across the Internet unified in their efforts or by compromised systems enlisted as 'zombies' that are controlled by servers, thereby providing anonymity to the controlling server of the attack. This scenario may require multiple RID traces, one to locate the zombies and an additional one to locate the controlling server. DDoS attacks do not necessarily spoof the source of an attack since there are a large number of source addresses, which make it difficult to trace anyway. DDoS attacks can also originate from a single system or a subset of systems that spoof the source address in packet headers in order to mask the identity of the attack source. In this case, an iterative trace through the upstream networks in the path of the attack traffic may be required. RID traces may also be used to locate a system used in an attack to compromise another system. Compromising a system can be accomplished through one of many attack vectors, using various techniques from a remote host or through a local privilege escalation attempts. The attack may exploit a system or application level vulnerability that may be the result of a design flaw or a configuration issue. A compromised system, as described above, can be used to later attack other systems. A single RID Relay Request may be used in this case since it is probable that the source address is valid. Identifying the sources of system compromises may be difficult since an attacker may access the compromised system from various sources. The attacker may also take measures to hide their tracks by deleting log files or by accessing the system through a series of compromised hosts. Iterative RID traces may be required for each of the compromised systems used to obscure the source of the attack. If the source address is valid, a Relay Request may be used in lei of a full RID Trace Request. System compromises may result from other security incidents types such as worms, Trojans, or viruses. It is often the case that an incident goes unreported even if valid source address information is available because it is difficult to take any action to mitigate or stop the attack. Incident handling is a difficult task for a NP and even at some client locations due network size and resource limitations. Moriarty Expires: April 21, 2005 [Page 7] Internet-Draft October 21, 2004 2. Recommended Network Provider (NP) Technologies For the purpose of this document, a network provider (NP) shall be defined as a backbone infrastructure manager of a network. The network provider's Computer Security Incident Response Team shall be referred to as the CSIRT. The backbone may be that of an organization providing network (Internet or private) access to commercial, personal, government, and educational institutions or the backbone provider of the connected network. The connected network provider is an extension meant to include Intranet and Extranet providers as well as instances such as a business or educational institute's, (etc.) private network. NPs typically manage and monitor their networks through a centralized network management system (NMS). The acronym NMS will be used to generically represent management servers on a network used for the management of network resources and the integration of RID messaging with other components of the network. This system may provide functions such as trend analysis for bandwidth utilization, report communication problems, and trigger a RID trace across the network or communicate with a RID system that can initiate a trace. The RID messaging system may be the same or a separate system from the NMS that communicates with various aspects of the network to coordinate incident response. The components of the network that may be integrated through the RID messaging system include attack or event detection, network tracing, and network devices to stop the effects of an attack. The detection of security incidents may rely on manual reporting, automated intrusion detection tools, and variations in traffic types or levels on a network. Intrusion detection system (IDS) may be integrated to the incident handling systems to create IODEF documents or RID messages to facilitate security incident handling. IDSs monitor network traffic analyzing packets to determine if the traffic might be classified as malicious. If an IDS detects malicious traffic, an analyst would determine the validity and severity of the attack traffic and if a trace is necessary. If the analyst determines a trace should be initiated, an IODEF document with RID extensions could be created or the necessary information sent to the RID messing system in order to create and track the attack traffic. Detection of a security incident is outside the scope of this paper, however it should be possible to integrate detection methods with RID messaging. Once a security incident has been identified the information is put into a RID message to integrate with the NP's single network trace mechanism. RID messaging is intended to be flexible in order to accommodate various trace systems currently in use as well as those that may evolve with technology. RID is intended to communicate the necessary information needed by a trace mechanism to the next upstream NP in the path of a trace. Therefore, a RID message must carry the superset of data required for all tracing systems. If Moriarty Expires: April 21, 2005 [Page 8] Internet-Draft October 21, 2004 possible, the trace may need to inspect packets to determine a pattern, which could assist reverse path identification. This may be accomplished by inspecting packet header information such as the source and destination IP addresses, ports, and protocol flags to determine if there is a way to distinguish them from other packets. A description of the incident along with any available automated trace data should trigger an alert to the NPs security team for further investigation. The various technologies used to trace traffic across a network are described in section 3.2. Another area of integration is the ability to mitigate or stop attack traffic once a source has been located. Any automated solution should consider the possible side effects to the network. A change control process or a central point for configuration management might be used to ensure that the security of the network and necessary functionality is maintained and that equipment configuration changes are documented. Automated solutions may depend upon the capabilities and current configuration management solutions on a particular network. The solutions may be based on authenticated and encrypted Simple Network Management Protocol (SNMP) or Network Configuration Protocol (NETConf) access to devices over an out-of-band connection or other similar technologies. 3. Characteristics of Attacks The goal of tracing a security incident may be to identify the source or to find a point on the network as close to the origin of the incident as possible. A security incident may be defined as a system compromise, a worm or Trojan infection, or a single or multiple source denial of service attack. Incident tracing can be used to identify the source(s) of an attack in order to cease or mitigate the undesired behavior. The communication system, RID, described in this paper can be used to trace any type of security incident and allows for actions to be taken when the source of the attack or a point closer to the source has been identified. The purpose of tracing an attack would be to cease or mitigate the affects of the attack through methods such as filtering or rate limiting the traffic close to the source or by using methods such as taking the host or network offline. Care must also be taken to ensure the system is not abused and to use proper analysis in determining if attack traffic is in fact attack traffic at each NP along the path of a trace. Tracing security incidents can be a difficult task since attackers go to great lengths to obscure their identity. In the case of a security incident, the true source might be identified due to an existing established connection to the attackers point of origin. However, the attacker may not connect to the compromised system for a long period of time after the initial compromise or may access the system through a series of compromised hosts spread across the network. Other methods of obscuring the source may include Moriarty Expires: April 21, 2005 [Page 9] Internet-Draft October 21, 2004 targeting the host with the same attack from multiple sources using both valid and spoofed source addresses. This tactic can be used to compromise a machine and leave a difficult task of locating the true origin for the administrators. DDoS attacks are also difficult or nearly impossible to trace because of the nature of the attack. Some of the difficulties in tracing these attacks include: O the attack originates from multiple sources, O the attack may include various types of traffic meant to Consume server resources, such as a SYN flood attack without a Significant increase in bandwidth utilization, O the type of traffic could include valid destination services, which cannot be blocked since they are essential services to business, such as DNS servers at an NP or HTTP requests sent to an organization connected to the Internet, O the attack may utilize varying types of packets including TCP, UDP, ICMP, or other IP protocols. O the attack may use a very small number of packets from any particular source, thus making a trace after the fact nearly impossible. If the source(s) of the attack cannot be determined from IP address information or tracing the increased bandwidth utilization, it may be possible to trace the traffic based on the type of packets seen by the client. In the case of packets with spoofed source addresses, it is no longer a trivial task to identify the source of an attack. In the case of an attack using valid source addresses, methods such as the traceroute utility can be used to fairly accurately identify the path of the traffic between the source and destination of an attack. If the true source has been identified, actions should be taken to cease or mitigate the effects of the attack by reporting the incident to the NP or the upstream NP closest to the source. In the case of spoofed source address other methods can be used to traceback to the source of an attack. The methods include packet filtering, packet hash comparisons, IP marking techniques, ICMP traceback, and packet flow analysis. As in the case of attack detection, tracing traffic across a single network is a function that can be used with RID in order to provide the networked ability to trace spoofed traffic to the source, while RID provides all the necessary information to accommodate the approach used on any single network to accomplish this task. RID can also be used to report attack traffic close to the source where the IP address used was determined to be valid. 3.1 Tracing a Distributed attack Tracing a DDoS attack is a very difficult problem. Since DDoS Moriarty Expires: April 21, 2005 [Page 10] Internet-Draft October 21, 2004 attacks may involve multiple sources with spoofed addresses, there may only be a small amount of traffic from each of the originating hosts. This makes it difficult to traceback to the sources. The sources may also alternate the type of traffic and the master may vary the sources from within the pool of sources launching the attack. Because of the dynamic nature of the DDos attack, immediate action would need to be taken to have any hope of locating the origin(s) of the attack with a near real-time trace. In order to identify a DoS attack or DDoS, a client may notify its NP that it is currently under attack. Automated methods might include statistical traffic analysis, which looks for unexpected fluctuations in bandwidth or in the size and types of packets sent between networks, hosts, or an IDS. There is on-going research in the area of detecting DoS and DDoS, and any effective techniques could be integrated with the tracing techniques described in this paper. Some research approaches include methods that detect backscatter traffic [9], using a data structure for bandwidth attack detection [10], and monitoring congestion through packet retransmission information [11]. Once an attack is suspected, traces would have to quickly identify the various sources of the attack. A generalized approach should be used to traceback connections using packet header information such as the destination IP address and any distinguishing header values of the traffic seen during the attack. The information collected along with an example packet would be used in a RID message to communicate incident handling information between NPs. 3.1.1 Tracing Security Incidents If a trace can identify the sources of a distributed attack, blocking the sources at the NP level close to the attacker could be an immediate action to stop the attack. In the case of a DDoS attack, further information may be obtained from the attacking computers as to the controller of the attack sending the 'zombies' control information to carry out the attack. A similar example of attack traffic with the possibility of multiple traces required would be one in which an attacker compromised a series of systems and accomplished hiding their source by logging into a string of systems to launch the attack. This additional trace is beyond the scope of this paper, but may use additional tracing mechanisms such as sniffing the network to locate the controllers of the attack. Finding a faster and more efficient way to trace multiple sources of an attack is essential to mitigating DDoS attacks. The ability to quickly relay and act upon the trace information gathered is imperative to stopping attack traffic. Tracing multiple attack paths can also cause additional stress on the network and does not scale well. A CSIRT report might be generated in the form an of IODEF document Moriarty Expires: April 21, 2005 [Page 11] Internet-Draft October 21, 2004 and then fed into a RID message or document to facilitate a trace or multiple traces of attack traffic. 3.2 Trace Approaches There have been many separate research initiatives to solve the problem of tracing upstream packets to detect the true source of attack traffic. Upstream packet tracing is currently confined to the borders of a network or a NP's network. Traces require access to network equipment and resources, which limit a trace to a specific network. Once a trace reaches the boundaries of a network, the network manager or NP adjacent in the upstream trace must be contacted in order to continue the trace. NPs have been working on individual solutions to accomplish upstream tracing within their own network environment. The tracing mechanisms implemented thus far have included proprietary or custom solutions requiring specific information such as IP packet header data, hash values of the attack packets, or marked packets. Hash values are used to compare a packet against a database of packets that have passed through the network in the case of 'Hash Based IP Traceback'[7]. Other research solutions involve marking packets as explained in 'ICMP Traceback Messages'[8], 'Practical Support for IP Traceback' [14], and IP Marking [1]. The following sections outline some available solutions for implementing traceback within the confines of a network managed by a single entity. The single network traceback solutions are discussed to determine the information needed to accomplish an inter-network trace where different solutions may be in place. 3.2.1 Trace approach via Traffic Flow Analysis Traffic flow analysis is used to monitor individual network traffic streams, such as a single TCP session beginning with the SYN packet and ending with the final FIN ACK in a session. There have been a few efforts to standardize flow analysis for network management, one through the traffic flow management MIB and another through NetFlow. The 'Traffic Flow Management' RFC [RFC2720] was designed to provide management information such as behavior models, Capacity planning, network performance, quality of service, and Attribution of network usage to system administrators. NetFlow from Cisco [5] provides similar capabilities to the traffic flow mib, except that it is specific to IP traffic and has already been implemented for traffic management in commercial off the shelf equipment. Although NetFlow was developed by Cisco, it is also an open standard. The flow analysis in both implementations can monitor with a capture filter on source and destination addresses, the number of packets and the count of bytes in each flow, the originating interface of the traffic, and the upstream peer information. The upstream peer information is essential to tracing a spoofed packet back to the true origin. There are several differences in the implementations and the Moriarty Expires: April 21, 2005 [Page 12] Internet-Draft October 21, 2004 monitor and capture capabilities of the two flow analysis implementations. NetFlow collects all packets and maintains the following information on packet flows for later analysis: O Source and destination IP address O Source and destination TCP/User Datagram Protocol (UDP) ports O Type of service (ToS) O Packet and byte counts O Start and end timestamps O Input and output interface numbers O TCP flags and encapsulated protocol (TCP/UDP) O Routing information (next-hop address, source autonomous system (AS) number, destination AS number, source prefix mask, destination prefix mask) Based on the information listed above, a spoofed packet can be traced upstream through a network to either identify the true source or the upstream peer. Various flow based solutions have been developed and implemented for use on a single backbone based on flow analysis and RID messaging must be able to support existing and future solutions to trace attacks across multiple networks. The AS number listed associated with a source IP address is only valid if the source IP address is valid. The AS number in this case cannot be trusted until the true source has been identified. 3.2.2 Trace Approach via Hash-Based IP Traceback BBN implemented a traceback solution, which collects hashes of IP packets across the network. The Hash-Based IP Traceback was designed specifically to trace attack traffic and achieve the following objectives O trace attacks after specific flows of the attack have completed O reduce storage requirements needed to save traceable packet data O provide a secure method to store packet captures on the Internet Hash-based IP traceback is another solution to provide the ability to trace attack traffic. By capturing all packets across the network and saving hash values for the IP header information that does not get altered as it traverses the network, attacks can be traced after the fact. Since hashes of IP header information are stored instead of the actual header information, privacy concerns are no longer an issue as might be the case with packet captures across the Internet. If a system used to store the packet captures was compromised, the data could not be used to identify which entities are 'talking' to each other on the Internet. BBN also considered how traces could be performed across a single network, for example an NP's backbone. The solution divides the network up into regions, each with its own collection station. The trace might be initiated at a particular collection station Moriarty Expires: April 21, 2005 [Page 13] Internet-Draft October 21, 2004 where data for a specific router is stored. When the collection station traces through its database for the matches of particular hashes of IP packets, it follows the trace through the network equipment for its own region. The collection station then determines which bordering region was the next upstream source of the attack and the trace is continued at the next collection agent. The trace continues until the source is identified or a neighboring network is identified as the upstream source of the attack. The upstream network must then be notified in some way in order to continue the trace. The upstream network will require the IP packet information in order to continue the trace. The upstream provider will want to look at its network and resources and decide if it would like to initiate a trace across their network. A limited number of packets can be stored based on resources and network traffic loads. RID is a possible solution for communicating the upstream Trace Request between bordering networks. 3.2.3 IP Marking IP Marking is another technique that can be used to trace attacks in which the source address has been spoofed in a more efficient manner than iterative trace mechanisms. This technique has been proposed specifically in terms of tracing DoS attacks across a network. All information is correlated at the end node or the target where the packets received would have been marked probabilistically along the path of the traffic. This method requires that routers and other infrastructure equipment have the ability to mark packets so that the path they tool can be derived at the destination address for the packets. Since all packets are not marked, depending on the IP Marking scheme used, a number of similar packets would have to be sent from a single source in order for it to be identified. IP Marking alone may not be a complete answer for tracing traffic, since an attacker could switch their methods to send very little data from any one host used in a DDoS attack, thus making it unlikely that enough packets will be marked to find the source of each stream. Integrating IP Marking with other techniques may be the best answer to ensure the efficiency and robustness of the system as a whole. In terms of integrating the IP Marking approach with RID there are several ways in which it may be useful. IP Marking may be used to gather information about the path of the trace up to an including identifying the actual source. A peer closer to the source might be identified if the IP Marking technique were not able to fully reconstruct the path of the trace. In this instance, the trace information could be sent to the closest point identified in the path from the IP Marking technique, thus shortening the length of time required to trace the traffic through the network. If a source was identified, a RID Relay Request might be used in order to trigger a specific action to take place close to the source to mitigate or stop the affects of the attack. Moriarty Expires: April 21, 2005 [Page 14] Internet-Draft October 21, 2004 4. Communication Between Network Providers Expediting the communication between NPs is essential when responding to a security related incident, which may cross network access points (Internet backbones) between providers. As a result of the urgency involved in this inter-NP security incident communication, there must be an effective system in place to facilitate the interaction. This communication policy or system should involve multiple means of communication to avoid a single point of failure. Email is one way to transfer information about the incident, packet traces, etc. However, email may not be received in a timely fashion or be acted upon with the same urgency as a phone call or other communication mechanism. Each NP should dedicate a phone number to reach a member of their security incident response team. The phone number could be dedicated to inter-NP incident communications and must be a hotline that provides a 24x7 live response. The phone line should reach someone who would have either the authority and expertise or the means to expedite the necessary action to investigate the incident. This may be a difficult policy to establish at smaller NPs due to resource limitations, so another solution may be necessary. An outside group may be able to serve this function given the necessary access to the NPs network. The outside resource should be able to mitigate or alleviate the financial and experience resource limitations. A technical solution to trace traffic across a single NP may include home grown or commercial systems in which RID messaging must accommodate the input requirements. The network management systems used on the NPs backbone to coordinate the trace across the single network requires a method to accept and process RID messages and relay trace requests to the system as well as wait for responses from the system to continue the RID request process as appropriate. In this scenario, each NP would maintain their own RID system and integrate with a management station used for network monitoring and analysis. An alternative for NPs lacking sufficient resources may be to have a neutral third party with access to the NPs network resources that could be used to perform the trace functions. This could be a function of a central organization operating as a computer response team for the Internet as a whole or within a consortium that may be able to provide centralized resources. Consortiums would consist of a group of NPs that agree to participate in the RID communication protocol with an agreed upon policy and communication protocol facilitating the secure transport of RID XML documents via SOAP. The first method described prevents the need to permit access to other network's equipment through the use of a standard messaging mechanism to enable RID or NMS's to communicate trace information to other networks in a consortium or in neighboring networks. The third party mentioned above may be used in this technical solution Moriarty Expires: April 21, 2005 [Page 15] Internet-Draft October 21, 2004 to assist in facilitating traces through smaller NPs. The messaging mechanism may be a logical or physical out-of-band network to ensure the communication is secure and unaffected by the state of the network under attack. The two management methods would accommodate the needs of larger NPs to maintain full management of their network and the third party option could be available to smaller NPs who lack the necessary human resources to perform a trace. The first method enables the individual NPs to involve their network operations staff to authorize the continuance of a trace through their network via a notification and alerting system. The out-of-band logical solution for messaging may be permanent virtual circuits configured with a small amount of bandwidth dedicated to RID communications between NPs. The network used for the communication, out-of-band or protected channels, would be direct communication links to transport RID messages, accepting only this messaging protocol. The communication links would be direct connections between network peers who have agreed upon use and abuse policies through the use of a consortium. Consortiums might be linked through policy comparisons and additional agreements to form a larger web or iterative network of peers that correlates to the traffic paths available over the larger web of networks. The maintenance of the individual links will be the responsibility of the two network peers hosting the link. Contact information, IP addresses of RID systems and other information must be coordinated between by a consortium and may use existing databases, such as the Routing Arbitor, as with any changes to the involved systems. The security, configuration, and confidence rating schemes of the RID messaging peers must be negotiated by peers and must meet certain overall requirements of the fully connected network, (Internet, government, education, etc.) through the peering and/or a consortium based agreement. RID messaging established with clients of an NP may be negotiated in a contract as part of a value added service or through a service level agreements. Further discussion is beyond the scope of this document and may be more appropriately handled in network peering or service level agreements. Procedures for incident handling need to be established and well known by anyone that may be involved in incident response. The procedures should also contain contact information for internal escalation procedures, as well as external assistance groups such as a CSIRT, CCCERT, GIAC, and the FBI. 4.1 Inter-Network Provider RID Messaging In order to implement a messaging mechanism between RID communication or NMS systems, a standard protocol and format is required to ensure inter-operability between vendors. The messages would have to meet several requirements in order to be meaningful Moriarty Expires: April 21, 2005 [Page 16] Internet-Draft October 21, 2004 as they traverse multiple networks. Real-Time Inter-Network Defense (RID) provides the framework necessary for communication between networks involved in the traceback and mitigation of a security incident. Several messages types described in section 4.2 are necessary to facilitate a trace across multiple networks. The message types include the Trace Request, Trace Authorization, Source Found, and Relay Request. A Trace Request message is used when the source of the traffic may have been spoofed. In that case, each network provider in the upstream path receives a trace request will issue a trace across their network to determine the upstream source of the traffic. The Trace Authorization and Source Found messages are used to communicate the status and result of a trace. The Relay Request message would only involve the RID communication systems along the path to the source of the traffic and not the use of single network trace systems. The Relay Request leverages the bilateral relationships or a consortium's interconnections to mitigate or stop problematic traffic close to the source. Routes would determine the fastest path to a known source IP address in the case of a Relay Request. A message sent between RID systems for a Trace Request or a Relay Request to stop traffic at the source through a bordering network would require the information enumerated below. 1. Enough information to enable the network administrators to make a decision about the importance of continuing the trace. 2. The filter or IP packet hash information needed to carry out the trace. 3. Contact information of the origin of the trace. The contact information could be provided through the autonomous system number [RFC1930] or NIC handle information listed in the Registry for Internet Numbers or other Internet databases. 4. Network path information to help prevent any routing loops through the network from perpetuating a trace. If a RID system receives a Trace Request containing its own information in the path, the trace must cease and the RID system should generate an alert to inform the network operations staff that a tracing loop exists. 5. A unique identifier for a single attack should to correlate traces to multiple sources in a DDoS attack. Use of the communication network and the RID protocol must be for pre-approved, authorized purposes only. It is the responsibility of each participating party to adhere to guidelines set forth in both a global use policy for this system as well as one established though the peering agreements for each bilateral peer or agreed upon consortium guidelines. The purpose of such policies are to avoid abuse of the system and shall be developed by a consortium of participating entities. The global policy may be dependent on the domain it operates under, for example, a government network or a commercial network such as the Internet would adhere to different guidelines to address the individual concerns. Privacy issues must be considered in public networks Moriarty Expires: April 21, 2005 [Page 17] Internet-Draft October 21, 2004 such as the Internet. Privacy issues are discussed in the security section along with other requirements that must be agreed upon by participating entities. Traces must be legitimate security related incidents and not used for purposes such as sabotage or censorship. An example of such abuse of the system would include a request to rate limit legitimate traffic to prevent information from being shared between users on the Internet (restricting access to online versions of papers) or restricting access from a competitor's product in order to sabotage a business. The RID system should be configurable to either require user input or automatically continue traces. This feature would enable a network manager to assess the available resources before continuing a trace. A trace may cause adverse affects on a network. If the confidence rating is low it may not be in the Network Provider's best interest to continue the trace. The confidence ratings must adhere to the specifications for selecting the percentage used to avoid abuse of the system. Trace Requests must be issued by authorized individuals from the initiating network, set forth in policy guidelines established through peering or SLA agreements. 4.2 RID Network Topology The most basic topology for communicating RID systems would be a direct connection or a bilateral relationship as illustrated below. __________ __________ | | | | | RID |__________-------------___________| RID | |_________| | NP Border | |________| ------------- Figure 1: Direct Peer Topology Within the consortium model, several topologies might be agreed upon and used. One would leverage bilateral network peering relationships of the members of the consortium. The peers for RID would match that of routing peers and the logical network borders would be used. This approach may be necessary for an iterative trace where the source is unknown. The model would look like the above diagram, however there may be an extensive number of inter- connections of bilateral relationships formed. Also within a consortium model, it may be useful to establish an integrated mesh of networks to pass RID messages. This may be beneficial where the source address is known and an interconnection may provide a faster route to reach the closest upstream peer to the source of the attack traffic. An example is illustrated below. Moriarty Expires: April 21, 2005 [Page 18] Internet-Draft October 21, 2004 _______ _______ ______ | | | | | | __| RID |____-------------____| RID |____-------------____| RID |__ |_____| | NP Border | |_____| | NP Border | |_____| | ------------- ------------- | |_______________________________________________________| Direct connection to network that is not an immediate network peer Figure 2: Mesh Peer Topology By using a fully meshed model in a consortium, broadcasting RID requests would be possible, but not advisable. By broadcasting a request, RID peers that may not have carried the attack traffic on their network would be asked to perform a trace for the potential of deceasing the time in which the true source was identified. As a result, many networks would have utilized unnecessary resources for a Trace Request that may have also been unnecessary. 4.3 Message Formats The following section describes the four RID message types which are based on the IODEF model. The messages are generated and received on RID communication systems on the NPs network. The messages may originate from IODEF messages from intrusion detection servers, CSIRTS, etc.. A RID message uses the IODEF framework with RID extensions in the AdditionalData class, which is encapsulated in a SOAP wrapper. Each RID message type is described in the following sections along with an example. SOAP [15] will be used as a wrapper with HTTPS or BEEP for the overlying transport to take advantage of existing standards for ease of implementation and integration of RID systems. Transport Layer Security (TLS) provides the necessary level of encryption for the transport RID messages. XML security functions such as digital signature and encryption provide the standards based methods to encrypt and digitally sign RID messages. RID messages specify system use and privacy guidelines through an extension to the IODEF model. Public Key Infrastructure (PKI) provides the base for authentication and authorization, encryption, digital signatures to establish trust relationships between members of a RID consortium or a peering consortium. XML security functions like the digital signature and encryption can be used within the contents of the message for privacy and security in cases where certain elements must remain encrypted or signed as they traverse the path of a trace. For example, the digital signature on a Trace Request can be used to verify the identify the trace originator. The use of the XML security features in RID messaging will be in accordance with the specifications for the IODEF model, however the use requirements may differ since RID also incorporates transport. Moriarty Expires: April 21, 2005 [Page 19] Internet-Draft October 21, 2004 4.3.1 RID Messages and Transport The four RID message types are: 1. Trace Request. This message is sent to the RID system next in the upstream trace. It is used to initiate a Trace Request or to continue a Trace Request to an upstream network closer to the source of the origin of the security incident. 2. Trace Authorization. This message is sent to the initiating RID system from each of the upstream NP's RID system to provide information on the trace status in the current network. 3. Source Found. This message is sent to the initiating RID system through the network of RID systems in the path of the trace as notification that the source of the attack was located. 4. Relay Request. This message type is used when the source of the traffic is believed to be valid. The purpose of the relay message request is to leverage the existing peer relationships in order to notify the network provider closest to the source of the valid traffic of a security related incident. When a system receives a RID message, it must be able to determine the type of message and parse it accordingly. The message type is specified in the RIDPolicy class extension to the IODEF model and is presented in the SOAP header. The details of the SOAP wrapper are discussed in section 6.7. For initial implementations, RID systems MUST support HTTPS for transport. BEEP and other means of transport are optional and the transport specifications will be defined in a separate document. Although HTTPS is not ideal for transport because of the overhead and the client server connection, the protocol is fully implemented and easy for initial integration with RID and SOAP. The transportation of messages will be described further in a transport related document. If HTTPS is used for transport, the Web Services Security Model may be used for an additional layer of security and policy settings. However, the baseline security and policy information MUST reside in the RID message itself as specified in this document. 4.3.2 RID Data Types RID is derived from the IODEF data model and inherits all of the data types defined in the IODEF model. With the exception of representing packet data, no other additional data types are required for RID extensions. The extension for RID containing the packet contents will be represented in a hexadecimal format for easier use by single network trace systems and integration with other aspects of the network. Hexadecimal data is defined in XML as the datatype: Moriarty Expires: April 21, 2005 [Page 20] Internet-Draft October 21, 2004 xs:hexBinary Hexadecimal attributes are represented by the hexBinary data type. The hexBinary data type allows binary content to be coded as a character string by translating the value of each binary octet into two hexadecimal digits. 4.3.4 IODEF-Document The IODEF model will be followed as specified in RFCXXXX (the RFC number will replace the XXXX when a number has been assigned for the document) for each of the RID message types. The AdditionalData class is used to define extensions to the IODEF- Document to facilitate RID communications. Each message type varies lightly in format and purpose; hence the requirements vary and will be specified for each. All classes, elements, attributes, etc. that are defined in the IODEF-Document are valid in the context of a RID-Document, however some listed as optional in IODEF are mandatory for RID as defined in sections 4.1.3. The IODEF model MUST be fully implemented to ensure proper parsing of all RID messages. Please see RFCxxxx for specific information on the IODEF-Document requirements. (The RFC number will be defined when the document becomes an RFC). 4.3.5 IODEF-Document Extensions There are four extensions required to facilitate RID communications within the IODEF data model. The IPPacket extension is used to represent the data used in tracing an incident, the NPPath extension is used to list out the path a trace has taken at The RIS system or NP level, the TraceStatus extension is used to indicate the approval status of a Trace or Relay Request, and the RIDPolicy extension is to facilitate the policy needs of RID. In order for network traffic to be traced across a network, an example packet from the attack must be sent along with trace or Relay Requests. All of the non-changing fields of an IP header along with 8 bytes of payload are required to provide enough information to uniquely trace the path of a packet. The non- changing fields of the packet header and the 8 bytes of payload are the superset of data required by most single network tracing systems used and prevent the need for sharing potentially sensitive information that may be contained in the data portion of a packet. The IODEF AdditionalData class will be used to create an XML document extension to include a hexadecimal formatted packet including all packet header information plus 8 bytes of payload. The complete header MUST be provided so that all systems expect a full packet header and can be properly parsed. The full content may be provided, but at least 8 bytes must be included to conduct a network trace. RID requires the first 28 bytes of an IP v4 packet Moriarty Expires: April 21, 2005 [Page 21] Internet-Draft October 21, 2004 in order to perform a trace. The required number of bytes provides the IP header in an IP V4 packet, which is 10 bytes long, the TCP/ UDP/ICMP header is also 10 bytes long, plus an additional 8 bytes of payload to distinguish the packet for tracing purposes. RID requires 48 bytes for an IP V6 packet in order to distinguish the packet in a trace. The input mechanism should be flexible enough to allow intrusion detection systems or packet sniffers to provide the information. The system creating the RID message should also use the packet information to populate the Incident class information in order to avoid human error, but also allow a system administrator to override the automatically populated information. As required for an IODEF extension in (IODEF Section 4.2), the parameter entities for extensions to the IODEF model are defined next. The definition, as defined in the IODEF DTD extension requirement, prior to the existence of the IODEF XML schema specification. It contains the locations of the RID extension DTDs and references the RID entities: %x-IPPacket; %x-NPPath; %x-TraceStatus; %x-RIDPolicy; ]> The AdditionalData class from the IODEF model is extended to facilitate RID communications as follows: +------------------+ | AdditionalData | +------------------+ | ANY | | |<>---{0..*)----[ IPPacket ] | ENUM restriction | | ENUM type |<>---{1..*}----[ NPPath ] | STRING meaning | | |<>---{0..1}----[ TraceStatus ] | | | |<>---{1..*)----[ RIDPolicy ] +------------------+ Figure 3: the AdditionalData class extension The aggregate classes that constitute the RID extensions for the AdditionalData class are: Moriarty Expires: April 21, 2005 [Page 22] Internet-Draft October 21, 2004 IPPacket Zero or many. The IP Packet that will be used to trace to the source of a security incident reported through RID. NPPath One or many. The contact information for the NPs involved in a trace, which includes information on the actual RID or NMS systems involved in the trace. TraceStatus Zero or One. This is used only in Trace Authorization messages to report back to the originating RID system if the trace will be continued by each RID system that received a Trace Request in the path to the source of the traffic. RIDPolicy One or many. The message type is specified as well as the policy setting to inform the NP receiving the Trace Request of the type of trace to be performed and if there may be regional or consortium related issues with continuing the Trace Request. This MUST be used in all RID traces and should be used in accordance with policy set between clients, peers, consortiums, and/or regions. Considerations of security, privacy, and confidentiality MUST be considered as specified in this document. The attributes of the AdditionalData class as defined in the IODEF model. Specific meanings have been added for use as strings in the meaning attribute. restriction optional. Defined in section 3.2 of the IODEF model. Type Required. ENUM. The data type of the element content. The permitted values for this attribute are in the IODEF document. The default value is "string", and MUST be set to "xml" for all extensions to the IODEF model as stated in the IODEF Data Model (Section 4.2). Meaning Mandatory. STRING. An identifier used to determine which extension of the AdditionalData attribute is used. In the context of RID, the following identifiers are valid: 1. RID-IPPacket. The packet information used to trace attack traffic used for RID incident response. 2. RID-NPPath. The Network Providers in the path of a trace that was either the origin of the request or a RID system in the path of the trace. 3. RID-TraceStatus. Trace Status is only used in the Trace Moriarty Expires: April 21, 2005 [Page 23] Internet-Draft October 21, 2004 Authorization message. It lists the response specifying if the trace will be continued from the upstream provider that received a Trace or Relay Request. The notification is sent to the originator of the request along with all NPs in the downstream path that has received the request. 4. RID-RIDPolicy. RIDPolicy MUST be included in all RID messages. Policy information as to the type of trace being requested, the destination of the message, and the possible boundaries for that trace. This is intended to ensure the trace reaches the correct RID messaging system, the request stays within the bounds acceptable by the defined use guidelines, and the data is protected at the appropriate level. Implementations MUST enforce use of the RIDPolicy extension. 4.3.5.1 IPPacket Extension The IPPacket information will be represented through the AdditionalData class extension of IODEF. +-----------------------+ | IPPacket | +-----------------------+ | ENUM restriction |<>-----------[ IPVersion ] | | | |<>-----------[ HexPacket ] | | | |<>---(0..*)--[ IPPacket ] +-----------------------+ Figure 4: the IPPacket class The aggregate classes that constitute the NPPath class are: IPVersion. One. STRING. The IP version of the packet used in the trace. 1. IPv4 2. IPv6 HexPacket. HexBinary. A packet in hexadecimal format using the xs:hexBinary XML data type. 28 bytes for an IPv4 packet. 48 bytes for an IPv6 packet. IPPacket Zero or many. Recursive definition of IPPacket, allowing for grouping of data. This may be used if more than one example packet will be sent in a single Trace or Relay Request. Moriarty Expires: April 21, 2005 [Page 24] Internet-Draft October 21, 2004 4.3.5.2 NPPath Extension The path information will also be an extension of the AdditionalData class. +------------------+ | NPPath | +------------------+ | ENUM restriction |<>---{0..1}----[ name ] | | | |<>---{0..*}----[ RegistryHandle ] | | | |<>-------------[ Node ] | | | |<>---{0..*}----[ Email ] | | | |<>---{0..*}----[ Telephone ] | | | |<>---{0..1}----[ Fax ] | | | |<>---{0..1}----[ Timezone ] | | | |<>---{1..*}----[ NPPath ] +------------------+ Figure 5: the NPPath class The aggregate classes that constitute the NPPath class are: name Zero or one. NAME. The name of the contact. The contact may either be an organization or a person. The type attribute dictates the semantics (organization or person). RegistryHandle Zero or many. The handle name in a registry. Care must be taken to ensure that a handle is meaningful to the recipient. Intra-organizational handles are of not much use for extra-organizational communication. The base definition is from IODEF section ***. Node One. The Node class is used to identify a host or network device, in this case to identify the system communicating RID messages or the NPÆs RID system. The base definition of the class is reused from the IODEF specification section 3.18. Email Zero or many. EMAIL. The email address of the contact formatted Moriarty Expires: April 21, 2005 [Page 25] Internet-Draft October 21, 2004 according to IODEF Section 2.2.12. Telephone Zero or many. PHONE. The telephone number of the contact formatted according to documentation in Section 5.21 of RFC2256. Fax Zero or one. PHONE. The facsimile telephone number of the contact formatted according to documentation in Section 5.21 of RFC2256. Timezone Zero or one. STRING. The timezone in which the contact resides. NPPath One or many. Recursive definition of NPPath, allowing for grouping of data. This is necessary in order to provide the complete list of systems communicating in the RID trace or relay request. The first NPPath definition is used for the originating host and NP information, the second listing is for the first NP that receives a request. All subsequent entries are used to list the information for each RID system for the NPs involved in the trace that a request has been sent to. 4.3.5.3 TraceStatus Extension The TraceStatus information will also use AdditionalData. +-------------------+ | TraceStatus | +-------------------+ | | | ENUM restriction |<>-------[ AuthorizationStatus ] | | +-------------------+ Figure 6: the TraceStatus class The aggregate elements that constitute the TraceStatus class are: AuthorizationStatus One. Required. ENUM. The listed values are used to provide a response to the requesting CSIRT of the status of a Trace Request in the current network. 1. Approved. The trace was approved and will begin in the current NP. 2. Denied. The trace was denied in the current NP. The next closest NP can use this message to filter traffic from the upstream NP using the example packet to help mitigate the effects of the attack as close to the source as possible. The Moriarty Expires: April 21, 2005 [Page 26] Internet-Draft October 21, 2004 Type 2 message must be passed back to the originator and a Type 3 used from the closest NP to the source to indicate actions taken. 3. Pending. Awaiting approval and a time-out period has been reached which resulted in this pending status and Type 2 message being generated. 4.3.5.4 RIDPolicy Extension The RIDPolicy information will also use AdditionalData. +-------------------+ | RIDPolicy | +-------------------+ | | | ENUM restriction |<>-------------[ MsgType ] | | | |<>---{1..*}----[ PolicyRegion ] | | | |<>-------------[ MsgDestination ] | | | |<>-------------[ Node ] | | | |<>---{1..*}----[ TrafficType ] +-------------------+ Figure 6: the RIDPolicy class The aggregate elements that constitute the RIDPolicy class are: MsgType One. Required. ENUM. The type of RID Message sent. The 4 types of messages are described in Section 4.2.1 and can be noted as one of the 4 selections below. 1. Trace Request. This message may be used to initiate a Trace Request or to continue a Trace Request to an upstream network closer to the source of the origin of the security incident. 2. Trace Authorization. This message is sent to the initiating RID system from each of the upstream RID systems to provide information on the trace status in the current network. 3. Source Found. This message indicates that the source of the attack was located and the message is sent to the initiating RID system through the RID systems in the path of the trace. 4. Relay Request. This message type is used when the source of the traffic is believed to be valid. The purpose of the relay Moriarty Expires: April 21, 2005 [Page 27] Internet-Draft October 21, 2004 message request is to leverage the existing peer relationships in order to notify the network provider closest to the source of the valid traffic of some event that has occurred, which may be a security related incident. MsgDestination One. Required. ENUM. The destination of the RID message will also appear in the NPPath extension, but may be encrypted in some cases. The destination required at this level may either be the RID messaging system intended to receive the request or the source of the incident in the case of a Relay Request where the RID system that can assist to stop or mitigate the traffic may not be known and the message has to traverse RID messaging systems by following the routing path to the closest RID system to the source of the attack traffic. The Node element lists either the RID system or the IP of the source and the meaning of the value in the Node element is determined by the MsgDestination element. 1. RID System. The address listed in the Node element of the RIDPolicy class is the next upstream RID system that will receive the RID message. 2. Source of Incident. The address listed in the Node element of the RIDPolicy class is the incident source. The IP address will be used to determine the path of RID systems that will be used to find the closest RID system to the source of an attack where the IP used by the source is believed to be valid and a Relay Request message is used. Node One. The Node class is used to identify a host or network device, in this case to identify the system communicating RID messages. The base definition of the class is reused from the IODEF specification IODEF 3.18. PolicyRegion One or many. Required. ENUM. The listed values are used to determine what policy area may require consideration before a trace can be approved. The PolicyRegion may include multiple selections from the list in order to fit all possible policy considerations when crossing regions, consortiums, or networks. 1. Client to NP. An enterprise network initiated the request. 2. NP to Client. An NP passed a RID request to a client or an enterprise attached network to the NP based on the service level agreements. 3. Inter-Consortium. A trace that should have no restrictions within the boundaries of a consortium with the agreed upon use and abuse guidelines. 4. Peer to Peer. A trace that should have no restrictions between Moriarty Expires: April 21, 2005 [Page 28] Internet-Draft October 21, 2004 two peers, but may require further evaluation before continuance beyond that point with the agreed upon use and abuse guidelines. 5. Between Consortiums. A trace that should have no restrictions between consortiums that have established agreed upon use and abuse guidelines. 6. Across National Boundaries. This selection must be set if the trace type is anything but a trace of attack traffic with malicious intent. This must also be set if the traffic request is based upon regulations of a specific nation that would not apply to all nations. This is different from the inter- consortium since it may be possible to have multiple nations as a member of the same consortium and this option must be selected if the traffic is of a type that may have different restrictions in other nations. TrafficType One or many. Required. ENUM. The listed values are meant to assist in determining if a trace is appropriate for the NP receiving the request to continue the trace. Multiple values may be selected for this element, however where possible, it should be restricted to one value which would most accurately describe the traffic type. 1. Attack. This option should only be selected if the traffic is related to a network based attack. The type of attack MUST also be listed in more detail in the IODEF Method and Impact classes for further clarification to assist in determining if the trace can be continued. 2. Network Related. This option MUST only be selected when the trace is related to NP network traffic or routing issues. 3. Content. This category MUST be used only in the case where the request is related to the content and regional restrictions on accessing that type of content exist. This is not malicious traffic, but may include determining what sources or destinations accessed certain materials available on the Internet including but not limited to news, technology, or inappropriate content. 4. Official Business. This option MUST be used if the traffic being traced is requested or affiliated with any government or other official business request. This would be used during an investigation by government authorities or other government traces to track suspected criminal or other activities, etc. 5. Other. If this option is selected, a description of the trace type MUST be provided so that policy decisions can be made to continue or stop the trace. The information should be provided in the IODEF message in the History Class using a HistoryItem log. 4.4 RID Documents Defined by Message Type Derived from IODEF This section includes the mandatory IODEF information used in all RID messages. Since RID is a wrapper for an IODEF document, the Moriarty Expires: April 21, 2005 [Page 29] Internet-Draft October 21, 2004 full IODEF specifications should be implemented, but the following section identifies the IODEF fields that must be filled in when generating a RID message or document. Other fields may optionally be filled in to provide further information to an incident handler and thus must be implemented for proper parsing of a RID message wrapping an IODEF document. This section will reference the IODEF model and the sections of the IODEF RFC where each IODEF class can be located. Incident Class (IODEF 3.2) Purpose: The Purpose will always be 1. Incident handling for RID. Restriction: Sender can select from the IODEF specifications for this value and fill in as appropriate IncidentID (IODEF 3.3) GUID: Name of CSIRT or NP that created the document Alternate ID (IODEF 3.4) This incident ID is one set by another CSIRT that is tracking the same or a similar incident. This value should not be set in the initial request, but may be set in a request passed forward by an NP in the path of a trace. Related Activity Class (IODEF 3.5) This class is optional if an AlternateID is specified, otherwise it is unnecessary. IncidentData Class (IODEF 3.7) Description: Text description of the incident - Mandatory for RID Assessment: Characterization of the impact - Mandatory for RID, (reference IODEF section 3.12) Impact aggregate class (IODEF 3.12.1) MUST be used along with the Confidence class (IODEF 3.12.5) in the Assessment Class. The other impact classes are optional and may depend on the Incident type to determine if the additional classes are appropriate. Method: Techniques used in attack - Mandatory for RID to determine the type of traffic for RIDPolicy information (IODEF 3.11) DetectTime: Mandatory for RID (Time Class - IODEF 2.26 and 3.9) StartTime: Mandatory for RID (Time Class - IODEF 2.26 and 3.9) EndTime: Optional for RID, incident may still be in process in which no end time can be listed (Time Class - IODEF 2.26, 3.9) ReportTime: Mandatory for RID (Time Class - IODEF 2.26 and 3.9) Contact: Mandatory for RID (IODEF 3.8) The required aggregate classes for the contact class in RID messages include: Name, RegistryHandle (IODEF 3.8.1), Email, Telephone The attributes in the contact class are required in the IODEF document and thus are required in RID messages and include: Restriction, Role, and Type Expectation: Mandatory for RID (IODEF 3.10) The StartTime and EndTime can be used to determine the type of Moriarty Expires: April 21, 2005 [Page 30] Internet-Draft October 21, 2004 trace that would be used on a network with multiple choices depending on the accuracy required. StartTime and EndTime to stop the trace would indicate if a fast or slower and more accurate method should be used for each Trace Request. The following attributes are required in RID messages: Priority and Category Note: Although Category is required in a request, the NP closest to the source of the attack decides upon the ultimate response. History: Required for upstream trace relays or requests, but not For the original request, (IODEF 3.13). May also be used to Further describe actions taken along the NP Path of a trace. EventData: Required for RID (IODEF 3.14 - 3.16) Much of the EventData Class is a duplicate for the aggregate IncidentData class and the proper uses of this class are defined in the IODEF RFC. System class (IODEF 3.17) The System class is required and the information listed in this class can be automatically entered into this class from the packet used in the incident trace by the RID implementation. Information must be reviewed by the submitter and the additional required classes and attributes filled in for proper processing of a request. The system class MUST be used to list the source and the target or intermediate system(s) and MUST note if the system was spoofed through the use of the Node class (IODEF 3.18). A separate instance of the System class (and Node Class) is used for each type of system listed in the document. The spoof section MUST be used in the System EventData Class of all RID messages and is set to the value of spoofed for all requests (Type 1) that require an actual trace of network traffic. In a Type 4 Relay Request, the source is believed to be valid. All other classes of the System Class are optional as in the IODEF document. AdditionalData: RID messages require that the NP Path and the IPPacket extensions are used to provide adequate information for an upstream peer to perform a trace. The information contained in the NPPath and IPPacket extensions must remain and be maintained in each RID message type document. The TraceStatus extension is used in message type 2 alone since it's purpose is to let the downstream NP know if the trace was approved and will begin in the next upstream network. IPPacket (IP version of packet to be traced) NPPath (Original Request should contain originator plus the next peer in the upstream request, the host that is receiving the request) TraceStatus (Approval status for the trace in the current network) RIDPolicy (Policy information for the Trace Request) Moriarty Expires: April 21, 2005 [Page 31] Internet-Draft October 21, 2004 Restriction Optional. ENUM. The IODEF restriction should be used in addition to the RID privacy and security guidelines since this is optional on the part of the receiving end of an IODEF message and is not enforced. Note: The implementation of the RID system may obtain some of the information needed to fill in the content required for each message type automatically from packet input to the system or default information such as that used in the NPPath extension. 4.4.1 Trace Request Description: This message or document is sent to the Network Management Station next in the upstream trace once the upstream Source of the traffic has been identified. The following information is required for message type 1 and will be provided through: RIDPolicy information Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incident Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) System Class is used to list both the Source and Destination Information used in the attack and must note if the traffic is spoofed, thus requiring an upstream Trace Request in RID Packet used to trace incident across the network IPPacket extension for RID Path information of RID systems used in the trace NPPath extension for RID Policy Information RID message number and destination RIDPolicy extension for RID [Free form test area for any additional information on justification for relay message request, IODEF IncidentData Description] Digital signature from initiating RID system, passed to all systems in upstream trace using XML digital signature A DDoS attack can have many sources resulting in multiple traces to locate the sources of the attack. It may be valid to continue multiple traces for a single attack. The path information would enable the administrators to determine if the exact trace had already passed through a single network. The incident identifier must also be used to identify multiple Trace Requests from a single incident. Moriarty Expires: April 21, 2005 [Page 32] Internet-Draft October 21, 2004 4.4.2 Trace Authorization Message Description: This message is sent to the initiating RID system from the next upstream NP's RID system to provide information on the trace status in the current network. The following information is required for Message Type 2 and will be provided through: RIDPolicy information Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incident Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) System class information Status of Trace Request TraceStatus extension for RID Packet used to trace incident across the network IPPacket extension for RID Path information of RID systems used in the trace NPPath extension for RID The last NP listed is the NP sending this Type 2 message. All previous NPs listed in the NPPath must be retained. Policy Information RID message number and destination RIDPolicy extension for RID [Additional free form text information on the attack, History Class] Digital signature of responding NP for authenticity of Trace Status Message, from the NP creating this message using XML digital signature A message is sent back to the initiating RID system of the trace as status notification. This message verifies that the next RID system in the path has received the message from the previous system in the path. This message also verifies that the trace is now continuing, has stopped, or is pending in the next upstream. The pending status would be automatically generated after a 2-minute timeout without system predefined or administrator action taken to approve or disapprove the trace continuance. Moriarty Expires: April 21, 2005 [Page 33] Internet-Draft October 21, 2004 4.4.3 Source Found Message Description: This message indicates that the source of the attack in this trace was located and is sent to the initiating RID system through the network of out-of-band RID systems in the path of the trace. The following information is required for message type 3 and will be provided through: RIDPolicy information Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incident Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) System Class is used to list both the Source and Destination Information used in the attack and must note if the traffic is spoofed, thus requiring an upstream Trace Request in RID Action Taken (Expectation and Category Class) Packet used to trace incident across the network IPPacket extension for RID Path information of RID systems used in the trace NPPath extension for RID The last NP listed is the NP, which located the source of the traffic (the NP sending the Type 3 message) Policy Information RID message number and destination RIDPolicy extension for RID [Free form test area for any additional information on The identified source of the attack traffic, IODEF Description, Incident Class] [True Source address and other information on the attack, History Class] Digital signature of source NP for authenticity of Source Found Message, the NP creating this message using XML digital signature A message sent back to the initiating RID system to notify the associated CSIRT that the source has been located. The actual source information may or may not be included depending on the policy of the network in which the client or host is attached. Any action taken by the NP to act upon the discovery of the source of a trace should be included. The NP may be able to automate the adjustment of filters at their border router to block outbound access for the machine(s) discovered as a part of the attack. The filters may be as comprehensive as to block all Internet access until the host has taken the appropriate action to resolve any security issues or to rate limit the ingress traffic as close to the source as possible, etc. Moriarty Expires: April 21, 2005 [Page 34] Internet-Draft October 21, 2004 Security and privacy considerations discussed in sections 6 and 7 must be taken into account. Note: The Category Class may be expanded in IODEF at a later date to accommodate all of the possible actions taken as a result of a RID Trace or Relay Request. Until that time occurs, the History class should be used to note all actions taken close to the source of a trace. The additional options include, but may not be limited to: Action Taken (multiple selections permitted) ______________________________________________ No action at this time Filter at upstream peer ingress point Rate Limit attack traffic Network segment blocked Host (IP Address) blocked from Internet access Protocol port used in attack blocked Alert generated Site notified Other 4.4.4 Relay Message Request Description: This message type is used when the source of the traffic is believed to be valid. The purpose of the relay message request is to leverage the existing bilateral peer relationships in order to notify the network provider closest to the source of the valid traffic of some event that has occurred, which may be a security related incident. The following information is required for Message Type 4 and will Be provided through: RIDPolicy information Time Stamps (DectectTime, StartTime, EndTime, ReportTime) Incident Identifier (Incident Class, IncidentID) Trace number - used for multiple traces of a single Incident, must be noted Confidence rating of Security Incident (Impact and Confidence Class) System Class is used to list both the Source and Destination Information used in the attack and must note if the traffic is spoofed, thus requiring an upstream Trace Request in RID Packet used to trace incident across the network IPPacket extension for RID Path information of RID systems used in the trace NPPath extension for RID Policy Information RID message number and destination RIDPolicy extension for RID Moriarty Expires: April 21, 2005 [Page 35] Internet-Draft October 21, 2004 [Free form test area for any additional information on justification for relay message request, IODEF Description] Digital signature from initiating RID system, passed to all systems in upstream trace using XML digital signature Security considerations would include the ability to encrypt the contents of the relay message request using the public key of the destination network provider. The incident number would increase as if it were a Trace Request message in order to ensure uniqueness within the system. The relaying peers would also append their AS information as the request message was relayed along the web of network providers so that the Source Found message could utilize the same path as set of trust relationships for the return message, which would indicate any actions taken. The request would also be recorded in both the state table of the initiating and destination NP RID system. The destination NP is responsible for any actions taken as a result of the request in adherence to any service level agreements or internal policies. The NP should confirm the traffic actually originated from the suspected system before taking any action and confirm the reason for the request. Note: The RIDPolicy extension information is necessary for all intermediate parties to access in order to properly direct the request packet and to route the Trace Authorization and source found messages back to the originator of the request. Moriarty Expires: April 21, 2005 [Page 36] Internet-Draft October 21, 2004 4.4.5 Example Upstream Trace The diagram below outlines the RID-DOS communication between RID systems on different networks tracing an attack. Attack Dest NP-1 NP-2 NP-3 Attack Src 1. Attack | Attack reported | detected 2. Initiate trace 3. Locate origin through upstream NP. 4. o---Msg-Type-1------> 5. Trace Initiated 6. <-----Msg-Type-2----o 7. Locate origin through upstream NP. 8. o---Msg-Type-1---> 9. Trace Initiated 10. <------------Msg-Type-2------------o 11. Locate attack source on network X 12. <------------Msg-Type-3------------o Figure 7: RID Communication Flow The NP that detected the attack initiates the trace. The attack is traced to the source or the next upstream NP. This process continues until the trace identifies the source of the attack. Any Trace Authorization and Source Found messages must pass through all RID systems in the path back to the trace initiator because of the secure connections established between RID systems of bordering networks. The involved systems in the path for Trace Authorization and Source Found messages would then have the ability to see and acknowledge the trace status before sending the messages back along the RID communication path to the originating RID system. Before a trace can be initialized, the originating RID system must check an internal database to determine if a trace to the same IP address or network address has occurred within a specified period of time, no less than 1 day. The trace may have been initiated by the same RID system or this RID system may have been in the path of the trace. The previous filter must be maintained for a minimum of a one-week period in order to retrieve the filter for comparison before initiating a Trace Request or allowing a trace continuance to occur. If the network administrator justifies a similar trace, a note might be added to the Description element of the document to Moriarty Expires: April 21, 2005 [Page 37] Internet-Draft October 21, 2004 provide an additional confidence indication to the upstream NPs in the path of the trace. A single network trace may be constrained using factors determined by the associated NP's network trace system in the path of the trace. The trace system may either trace a packet in real time or search through stored packet data for evidence that the packet had traversed the network. In the case of a real time trace, the traffic needs to be active on the network for the trace to be successful or the trace will cease. A message is sent to indicate the status, that the trace cannot continue, to the originating RID system through the consortium's trust relationships formed by the RID systems in the path of the trace. The packet trace may also be limited due to the lack of storage space on networks, for saving traffic data. A Trace Authorization message is sent, in this case as well, to provide the path information up to the point in which the trace could no longer be continued to the originator of the trace through the RID systems in the path of the trace. This information could also be used to block or mitigate the traffic at the participating NP closest to the source. 4.4.6 RID Trace Request Example The example listed is of a Trace Request, based on the incident report example from the IODEF document. The AdditionalData extensions were added as appropriate for a Trace Request message using the IPPacket and NPPath classes. The example given is that of a CSIRT reporting a DoS attack in progress to the upstream NP. The request asks the next NP to continue the trace and have the traffic mitigated closer to the source of the traffic. CERT-FOR-OUR-DOMAIN#207-1 Host involved in DOS attack 2004-02-02T22:19:24+00:00 2004-02-02T22:49:24+00:00 2004-02-02T23:20:24+00:00 Rate limit traffic close to source CSIRT-FOR-OUR-DOMAIN csirt-for-our-domain@ourdomain Moriarty Expires: April 21, 2005 [Page 38] Internet-Draft October 21, 2004 Constituency-contact for 10.1.1.2 Constituency-contact@10.1.1.2 CSIRT-FOR-OUR-DOMAIN#207-1 CERT-FOR-OUR-DOMAIN Notification sent to next upstream NP closer to 10.1.1.2 2001-09-14T08:19:01+00:00 38765
10.1.1.2
 80
192.168.1.2
 xmlns:RID="http://www.ietf.org/iodef/RID-Policy.html" xmlns="http://www.ietf.org/iodef/RID-Policy.html"> 1 3 1
172.20.1.2
 1 Moriarty Expires: April 21, 2005 [Page 39] Internet-Draft October 21, 2004 xmlns:RID="http://www.ietf.org/iodef/RID-IPPacket.html" xmlns="http://www.ietf.org/iodef/RID-IPPacket.html"> IPv4 450000522ad90000ff06c41fc0a801020a010102976 d0050103e020810d94a1350021000ad6700005468616e6b20796f7 520666f72206361726566756c6c792072656164696e67207468697 3205246432e0a xmlns:RID="http://www.ietf.org/iodef/RID-NPPath.html" xmlns="http://www.ietf.org/iodef/RID-NPPath.html"> CSIRT-FOR-OUR-DOMAIN CSIRT123 csirt-for-our-domain@ourdomain
172.17.1.2
 CSIRT-FOR-UPSTREAM-NP CSIRT345 csirt-for-upstream-np@ourdomain
172.20.1.2
 <-- Digital Signature applied to the IPPacket class using the XML Digital Signature W3C Recommendations. --> IPv4 450000522ad90000ff06c41fc0a801020a010102976d0050103e0 20810d94a1350021000ad6700005468616e6b20796f7520666f72206 361726566756c6c792072656164696e672074686973205246432e0a Moriarty Expires: April 21, 2005 [Page 40] Internet-Draft October 21, 2004 KiI5+6SnFAs429VNwsoJjHPplmo= VvyXqCzjoW0m2NdxNeToXQcqcSM80W+JMW+Kn01cS3z3KQwCPeswzg==

/KaCzo4Syrom78z3EQ5SbbB4sF7ey80etKII864WF64B81uRpH5t9j QTxeEu0ImbzRMqzVDZkVG9xD7nN1kuFw==

li7dzDacuo67Jg7mtqEm2TRuOMU= Z4Rxsnqc9E7pGknFFH2xqaryRPBaQ01khpMdLRQnG541Awtx/XPaF5 Bpsy4pNWMOHCBiNU0NogpsQW5QvnlMpA== VFWTD4I/aKni4YhDyYxAJozmj1iAzPLw9Wwd5B+Z9J5E7lHjcAJ+bs HifTyYdnj+roGzy4o09YntYD8zneQ7lw== --> 5. RID IODEF Extension Document Type Definition Moriarty Expires: April 21, 2005 [Page 41] Internet-Draft October 21, 2004 Moriarty Expires: April 21, 2005 [Page 42] Internet-Draft October 21, 2004 5.1 RID Schema Definition with IODEF Schema Imported Moriarty Expires: April 21, 2005 [Page 44] Internet-Draft October 21, 2004 Moriarty Expires: April 21, 2005 [Page 45] Internet-Draft October 21, 2004 Moriarty Expires: April 21, 2005 [Page 46] Internet-Draft October 21, 2004 6. Message Transport RID messages or documents can be transported over existing protocols since the messages are in an XML format using the IODEF model. The privacy and security considerations are such that a means to encrypt and sign the data must be provided. Encrypting or signing the documents may be done within the capabilities of XML, as defined in the IODEF specification. SOAP will be used as a wrapper around the RID message with HTTPS as a mandatory implementation for transport. The support of other transport protocols to encrypt data such as BEEP and S/MIME are encouraged. Transport protocols must use encryption to provide an additional level of security, integrity, and authentication through bi-directional certificate usage. The encryption requirements and considerations for RID are discussed in the Security section of this document. 6.1 Message Delivery Protocol - Integrity and Authentication The RID protocol must be able to guarantee delivery and meet the necessary security requirements of a state-of-the-art protocol. In order to guarantee delivery, TCP should be considered as the underlying protocol within the current network standard practices. It may seem appropriate to use SNMP trap messages since Network Management Systems already use this messaging structure. However, RFC1215 discourages the use of traps for this type of application and attempts to discourage the creation of new trap types. The current trap messaging structure does not satisfy the information requirements in order to successfully carry out a trace. Trap messages are sent via UDP, which assist in the quick delivery of packets, however they do not guarantee delivery as in TCP. The RID protocol for inter-network communication could provide the transport mechanism for message delivery. Security considerations must include the integrity, authentication, privacy, and authorization of the messages sent between RID communication or NMS systems. The communication between RID systems must be authenticated and encrypted to ensure the integrity of the messages and the RID systems involved in the trace. Another concern that needs to be addressed is authentication for a request that traverses multiple networks. In this scenario, systems in path of the multi-hop Trace Request need to authorize a trace from not only their neighbor network, but also from the initiating RID system as discussed in section 6.3. Several methods can be used to ensure integrity and privacy of the communication. The transport mechanism selected (HTTPS, S/MIME, BEEP, etc.) may be agreed upon by a consortium using the RID protocol to ensure consistency among the peers. Consortiums may vary their selected transport mechanisms and thus must decide up on a mutual protocol to use for transport when communicating with peers in a neighboring consortium using RID. RID systems MUST support HTTPS and Moriarty Expires: April 21, 2005 [Page 47] Internet-Draft October 21, 2004 optionally support other protocols such as S/MIME and BEEP. RID, the XML security functions, and transport protocols must properly integrate with a public key infrastructure (PKI) managed by the consortium. Consortiums are discussed in the security and privacy sections. 6.2 Transport Communication Out-of band communications dedicated to NP interaction for RID messaging would provide additional security as well as guaranteed bandwidth during a denial of service attack. For example, an out-of-band channel may consist of logical paths defined over the existing network. Out-of-band communications may not be possible between all network providers, but should be considered to protect the network management systems used for RID messaging. In order to address the integrity and authenticity of messages, transport encryption MUST be used to secure the traffic sent between RID systems with pre-defined trust relationships. Systems with predefined relationships for RID would include those who peer within a consortium with agreed upon appropriate use regulations and for peering consortiums. Systems used to send authenticated RID messages between networks MUST use a dedicated and secured interface to connect to a border Network's RID systems. Each connection to a RID system must meet the security requirements agreed upon through the consortium regulations, peering, or service level agreements (SLA). The RID system interface must only listen for and send RID messages, which also must be over an encrypted tunnel meeting the minimum requirement of algorithms and key lengths established by the consortium, peering, or SLA agreement. The selected algorithm must meet minimum security levels of the times, 3DES or 128-bit AES are sufficient at the time this document was written. The encryption strength must adhere to import and export regulations of the involved countries for data exchange. 6.3 Authentication of RID Protocol In order to insure the authenticity of the RID messages, a message authentication scheme using a public key infrastructure (PKI) must be inherent to the protocol. SOAP tied together with TLS used with BEEP or HTTP(S) using WS-Security requires a trust center such as a PKI or Kerberos key distribution center for the distribution of credentials to provide the necessary levels of security for this protocol. Public key certificates pairs issued by a trusted Certificate Authority (CA) will be used to provide the necessary level of authentication and encryption for the RID protocol. The CA used for RID messaging must be trusted by all involved parties and may take advantage of similar efforts, such as the Internet2 federated PKI. The PKI infrastructure used for authentication would also provide the necessary certificates needed Moriarty Expires: April 21, 2005 [Page 48] Internet-Draft October 21, 2004 for encryption via either Transport Layer Security (TLS) used in the HTTPS protocol, BEEP profile, or Secure MIME (S/MIME). Hosts receiving a RID message, such as a Trace Request, for example, must be able to verify that the sender of the request is valid and trusted. Using digital signatures on a hash of the RID message with an X.509 version 3 certificate issued by a trusted party can be used to authenticate the request. The X.509 version 3 specifications as well as the digital signature specifications and Certificate Revocation List (CRL) Internet standards set forth in RFC2459 must be followed in order to interoperate with a PKI designed for similar Internet purposes. The IODEF specification must be followed for digital signatures to provide the authentication and integrity aspects required for secure messaging between network providers. The use of digital signatures in RID XML messages MUST follow the World Wide Web Consortium (W3C) recommendations for signature syntax and processing when either the XML encryption or digital signature are used within a document. Transport specifications will be detailed in a separate document. An optional extension to the authentication scheme would be to incorporate the use of attribute certificates to provide authorization capabilities as described in RFC3281. This may be useful as messages are sent from network peers to determine authorization levels based on the attribute information in the certificate, which could be used to determine priority of a trace request. The attribute information might be used to determine if a Trace Request should be processed automatically or if human intervention is required. 6.4 Authentication Considerations for a Multi-hop Trace Request Bilateral trust relations between network providers ensure the authenticity of requests for Trace Requests from immediate peers in the web of networks formed to provide the traceback capability. A network provider several hops into the path of the RID trace must trust the information from their peer as to the confidence rating of the attack and the previous trust relationships in the downstream path. In order to provide a higher assurance level as to the authenticity of the Trace Request, the originating RID system is included in the Trace Request along with contact information as well as the information of all RID systems in the path the trace has taken. A second measure must be taken to ensure the identity of the originating RID system. The originating RID system MUST include a digital signature in the Trace Request sent to all systems in the upstream path. The digital signature from the RID system is performed on the IPPacket class of the RID extension to the IODEF model in the AdditionalData class following the XML digital signature specifications from W3C [22]. The signature MUST be Moriarty Expires: April 21, 2005 [Page 49] Internet-Draft October 21, 2004 passed to all parties that receive a Trace Request and each party MUST be able to perform full path validation on the digital signature. Full path validation verifies the chaining relationship to a trusted root and also performs certificate revocation status. In order to accommodate that requirement, the IPPacket class data MUST remain unchanged as a request is passed along between providers and is the only element for which the signature is applied. A second benefit to this requirement is that the integrity of the filter used is ensured as it is passed to subsequent NPs in the upstream trace of the packet. The trusted PKI used in section 6.3 will also provide the keys used to digitally sign the IPPacket class in the Trace Requests to meet the requirement of authenticating the original request. Since the CA is known and trusted by all parties, any host in the path of the trace can verify the digital signature. In the case where an enterprise network using RID sends a trace request to their provider, the signature from the enterprise network must be included in the initial request. The NP may generate a new request to send upstream to members of the NP consortium to continue the trace. If the original request is sent, the originating NP, acting on behalf of the enterprise network under attack, must also digitally sign the message to assure the authenticity of the trace. An NP that offers RID as a service may be using their own PKI to secure RID communications between their RID system and the attached enterprise networks. NPs participating in the trace must be able to determine the authenticity of RID requests at the NP level. 6.4.1 Public Key Infrastructures and Consortiums Consortiums of NPs are an ideal way to establish a communication web of trust for RID messaging. The consortium could provide centralized resources, such as a PKI, and established guidelines for use of the RID protocol. The consortium would also assist in establishing trust relationships between the participating NPs to achieve the necessary level of cooperation and experience sharing among the consortium entities. The consortium may also be used for other purposes to better facilitate communication among NPs in a common area (Internet, region, government, education, private networks, etc.). Using a PKI to distribute certificates used by RID systems provides an already established method to link trust relationships between NPs of consortiums that would peer with NPs belonging to a separate consortium. In other words, consortiums could peer with other consortiums to enable communication of RID messages between the participating NPs. The PKI along with Memorandum of Agreements could be used to link border directories to share public key information in a bridge, hierarchy, or a single cross certification relationship. Moriarty Expires: April 21, 2005 [Page 50] Internet-Draft October 21, 2004 Consortiums also need to establish guidelines for each participating NP to adhere to. The guidelines MUST include: O Physical and practices to protect RID systems O Network and application layer protection for RID systems and communications O Proper use guidelines for RID systems, messages, and requests O A PKI to provide authentication, integrity, and privacy PKI can also provide the same level of security for communication between an end entity (enterprise, educational, government customer network) and the NP. The PKI may be a subordinate CA or in the CA hierarchy from the NPs consortium to establish the trust relationships necessary as the request is made to other connected networks. 6.5 Privacy Concerns and System Use Guidelines Privacy issues raise many concerns when information sharing is required to achieve the goal of stopping or mitigating the affects of a security incident. The IODEF extension, RIDPolicy will be used to automate the enforcement of the privacy concerns listed within this document. The privacy and system use concerns that MUST be addressed in the RID system and other integrated components include: Network Provider Concerns: o Privacy of data monitored and/or stored on IDS for attack detection o Privacy of data monitored and stored on systems used to trace traffic across a single network Customer attached networks participating in RID with NP: O Customer networks may include enterprise, educational, government or other attached network to an NP participating in RID and MUST be made fully aware of the security and privacy considerations for using RID. O Customers MUST know the security and privacy considerations in place by their NP and the consortium of which the NP is a member. O Customers MUST understand that their data can and will be sent to other NPs in order to complete a trace unless an agreement stating otherwise is made in the service level agreements between the customer and NP. Parties Involved in the Attack: o Privacy of the identity of a host involved in an attack o Privacy of information such as the source and destination used for communication purposes over the monitored or RID connected Moriarty Expires: April 21, 2005 [Page 51] Internet-Draft October 21, 2004 network(s) o Protection of data from being viewed by intermediate parties in the path of a Relay Request MUST be considered Consortium Considerations: o System use restricted to security incident handling within the local regions definitions of appropriate traffic for the network monitored and linked via RID in a single consortium also abiding by the consortiums use guidelines o System use prohibiting the consortiums participating NPs from inappropriately tracing non attack traffic to locate sources or mitigate traffic unlawfully within the jurisdiction or region Inter-Consortium Considerations: o System use between peering consortiums MUST also adhere to any government communication regulations that apply between those two regions, such as encryption export and import restrictions o System use between consortiums MUST not request traffic traces and actions beyond the scope intended and permitted by law or inter-consortium agreements o System use between consortiums MUST respect national boundary issues and limit requests to appropriate system use and not to achieve their own agenda to limit or restrict traffic that is otherwise permitted within the country in which the peering consortium resides RID is useful in determining the true source of a packet that traverses multiple networks or to communicate security incidents and automate the response. In order to identify the source and trace multiple networks, the packet header information along with 8 bytes of payload are used in the packet identification. The information obtained from the trace may determine the identity of the source host or the network provider used by the source of the traffic. It should be noted that the trace mechanism used across a single network provider may also raise privacy concerns for the clients of the network. Methods that may raise concern include those which involve storing packets for some length of time in order to trace packets after the fact. Monitoring networks for intrusions and for tracing capabilities also raise concerns for potentially sensitive valid traffic that may be traversing the monitored network. IDS and single network tracing is outside of the scope of this document, but the concern should be noted and addressed within the use guidelines of the network. Some IDS and single network trace mechanisms attempt to properly address these issues. RID is designed to provide the information needed by any single network trace mechanism. The providers choice of a single trace mechanism depends on resources, existing solutions, and local legislation. Privacy concerns in regard to the single network trace must be Moriarty Expires: April 21, 2005 [Page 52] Internet-Draft October 21, 2004 dealt with at the client to network provide level and are out of scope for RID messaging. The identity of the true source of an attack packet being traced through RID could be sensitive. The true identity listed in a Source Found message can be protected through the use of encryption on the fields containing the identity, using the public encryption key for the originating NP. Alternatively, the action taken may be listed without the identity being revealed to the originating NP. The ultimate goal of the RID communication system is to stop or mitigate attack traffic, not to ensure the identity of the attack traffic is known to involved parties. The NP that identifies the source needs to deal directly with the involved parties and proper authorities in order to determine the guidelines for the release of such information, if it is regarded as sensitive. In some situations, systems used in attacks are compromised by an unknown source and, in turn, are used to attack other systems. In that situation, the reputation of a business or organization may be at stake and the action taken may be the only additional information reported in the Source Found message to the originating system. If the security incident is a minor incident, such a zombie system used in part of a large-scale DDoS attack, ensuring the system is taken off the network until it has been fixed may be sufficient. The textual descriptions should include details of the incident in order to protect the reputation of the unknowing attacker and prevent the need for additional investigation. Local, state, or national laws may dictate the appropriate reporting action for specific security incidents. Privacy becomes an issue whenever sensitive data traverses a network. For example, if an attack occurred between a specific source and destination, then every network provider in the path of the trace would become aware that the cyber attack occurred. In a targeted attack, it may not be desirable for the information that two nation states are battling a cyber war to become general knowledge to all intermediate parties. However, it is important to allow the traces to take place in order to cease the activity since the health of the networks in the path could also be at stake during the attack. This provides a second argument for allowing the Source Found message to only include an action taken and not the identity of the offending host. In the case of a Relay Request, where the originating NP is aware of the NP that will receive the request for processing, the free form text areas of the document could be encrypted using the public key of the destination NP to ensure that no other NP in the path can read the contents. The encryption would be accomplished through the W3C specifications for encrypting an element. In some situations, all network traffic of a nation may be granted through a single network provider. In that situation, options must support sending Source Found messages from a downstream peer of that network provider. That option provides an additional level of Moriarty Expires: April 21, 2005 [Page 53] Internet-Draft October 21, 2004 abstraction to hide the identity and the NP of the identified source of the traffic. Legal action may override this technical decision after the trace has taken place, but that is out of the technical scope of this document. Privacy concerns when using a Relay Request to request action close to the source of valid attack traffic needs to be considered. Although the intermediate NPs relay the request to the closest NP to the source, the intermediate NPs do not require the ability to see the contents of the packet or the text description field(s) in the request. This message type does not require any action by the intermediate RID systems, except to relay the packet to the next NP in the path. Therefore, the contents of the request may be encrypted. The intermediate NPs would only need to know how to direct the request to the manager of the AS number in which the source IP address belongs. Traces must be legitimate security related incidents and not used for purposes such as sabotage or censorship. An example of such abuse of the system would include a request to block or rate limit legitimate traffic to prevent information from being shared between users on the Internet (restricting access to online versions of papers) or restricting access from a competitor's product in order to sabotage a business. Inter-consortium RID communications raise additional issues especially where the peering consortiums reside in different regions or nations. Trace Requests and requested actions to mitigate traffic must adhere to the appropriate use guidelines and yet prevent abuse of the system. First, the peering consortiums MUST identify the types of traffic that can be traced between the borders of the participating NPs of each consortium. The traffic traced should be limited to security incident related traffic. Second, the traces permitted within one consortium if passed to a peering consortium may infringe upon the peering consortium's freedom of information laws. An example would a consortium in one country may permit a trace of traffic containing objectionable material, outlawed within that country. The RID trace may be a valid use of the system within the confines of that country's network border, however, it may not be permitted to continue across network boundaries where such content is permitted under law. By continuing the trace in another country's network the trace and response could have the effect of improperly restricting access to data. A continued trace into a second country may break the laws and regulations of that nation. Any such traces MUST cease at the country's border. The privacy concerns listed in this section have addressed issues of privacy among the trusted parties involved in a trace within an NP, a RID consortium, and peering RID consortiums. Data used for RID communications must also be protected from parties that are not trusted. This protection is provided though the Moriarty Expires: April 21, 2005 [Page 54] Internet-Draft October 21, 2004 authentication and encryption of documents as they traverse the path of trusted servers. Each RID system MUST perform a bi-directional authentication when sending a RID message and use the public encryption key of the upstream or downstream peer to send a message or document over the network. This means that the document is decrypted and re-encrypted at each RID system either via S/MIME or TLS over BEEP or HTTPS. The RID messages must be decrypted at each RID system in order to properly process the request or relay the information. Today's processing power is more than sufficient to handle the minimal burden of encrypting and decrypting relatively small typical RID message. 6.7 SOAP Wrapper RID messages must use a SOAP wrapper. The transport is independent of the wrapper. SOAP will be used to provide the messaging framework and can make distinctions as to how messages should be handled by each RID system. SOAP has also been selected because of the flexibility it provides for binding with transport protocols, which can be independent of the RID messaging system. As defined by the SOAP messaging specifications [18], the RID document will be in the SOAP body of the message. The SOAP header contains information that is pertinent to all RID systems that receive the message, including the ultimate destination and the intermediate hosts. Therefore, the elements or classes needed by all RID system MUST be in the SOAP header, specifically the RIDPolicy class. The information in the Incident class is not required in the header since it is not necessary for intermediate RID systems in order to make decisions, such as the type of trace to perform. The destination information for the message is contained in the RIDPolicy class, either the source IP address of the attack or the RID system to receive the message. If a relay request is received by an intermediate SOAP node, the RIDPolicy class has the information necessary to forward the request to a RID messaging system that serves as the ultimate destination. The ultimate destination is the system closest to the IP address identified as the source of the incident. The RID system determined to be the ultimate destination will parse the full message so the incident information can be evaluated. Each RID system receiving a Trace Request is an ultimate destination and has to parse and view the entire RID document to make necessary decisions. The SOAP specifications for intermediate and ultimate nodes MUST be followed, for example a message destined for an intermediate node would contain the attribute env:role with the value http://www.w3c.org/2003/05/soap-envelope/role/next. Also in accordance with the SOAP specifications, the attribute of env:mustUnderstand has a value of "true" to ensure each node processes the header blocks consistent with the specifications for RID. Moriarty Expires: April 21, 2005 [Page 55] Internet-Draft October 21, 2004 SOAP messages are typically are a one-way conversation and communication is created by the application, in this case RID. The bi-directional communication is formed by responses to trace requests used to confirm trace continuance or action taken when a source has been identified. The RIDPolicy elements listed in the SOAP header for directing messages and the communication flow is outlined below for each message type. Trace Request - The next RID system will be listed in the RIDPolicy So the full message is parsed and evaluated. A response may be a Trace Request in the next upstream network, a Trace Authorization, or a Source Found message. Trace Authorization - The RIDPolicy will list the previous RID system in the path of the trace as the destination. Participating RID systems in the upstream trace MUST see the trace status. The previous RID system must know whether or not the trace was continued. If the trace was not continued, action may be taken to mitigate the effects of the attack at the previous NP. The originator of the request MUST also see all of the Trace Authorization messages to obtain status information on the trace. The neighbor RID system may send the request directly to the originator. If any RID systems in the path of the message are used as intermediate systems because of established trust relationships, they do not need to parse the message. Source Found - The Source Found lists the originator of the request as the destination and since that RID system is the only one that needs to process the message. The message body may be encrypted for confidentiality of the incident information using the public key of the originating RID system. The systems in the path are viewed as intermediate SOAP nodes. Relay Request - The RIDPolicy for a Relay Request contains the IP address of the source of the security incident, which is used to route the request. The systems used to route the message are treated as intermediate SOAP nodes. The message is parsed and evaluated by the RID system responsible for the IP address of the incident source which is the ultimate destination of the SOAP message. The SOAP binding will be used for message transport. One agreed upon protocol, HTTPS, MUST be implemented by all RID systems and other protocols may be used. 7. Security Considerations Communication between NP's RID systems must be protected. An out of band network, either logical or physical would prevent outside attacks against RID communication. An out of band connection would be ideal, but not necessarily practical. Authenticated encrypted tunnels between RID systems MUST be used to provide Moriarty Expires: April 21, 2005 [Page 56] Internet-Draft October 21, 2004 confidentiality, integrity, authenticity, and privacy for the data, therefore MUST be used. Trust relationships are based on consortiums and established trust relationships of PKI cross certifications of consortiums. By using SOAP, RID Policy information, Transport Layer Security, and the XML security features of encryption and digital signatures, RID takes advantage of existing security standards. The standards provide clear methods to ensure messages are secure, authenticated, authorized, meet policy and privacy guidelines, and integrity is maintained. As specified in the relevant sections of this document, the XML digital signature and XML encryption are used in the following cases: XML Digital Signature O Originator of the Trace or Relay Request MUST sign the IPPacket class data to provide authentication to all upstream participants in the trace of the origin. This signature MUST be passed to all recipients of the Trace Request. O For all message types, the full RID message must be signed by the sending peer to provide authentication and integrity for the next upstream NP involved in the trace XML Encryption O The entire request may be encrypted to provide an extra layer of security between peers so that the message is not only encrypted for the transport, but also while stored. This behavior would be agreed upon between peers, a consortium or determined on a per message basis based on security requirements. The RIDPolicy extension would be provided in clear text in the SOAP header. O A Relay Request may be encrypted for the intended recipient if the RID network is being used for message transfer and the intermediate parties do not need to have knowledge of the request contents. In that case, the RIDPolicy extension is used by intermediate parties and is maintained in the SOAP header in clear text. O The action taken in the Source Found message may be encrypted using the key of the request originator. In that case, the intermediate parties can view the RIDPolicy information and know the trace has been completed and do not need to see the action. If the use of encryption were limited to sections of the message, the history class and category class would be encrypted. Otherwise, the entire message with the exception of the RIDPolicy information and incident identifier could be encrypted for the originator of the request. Intermediate parties used in the path of the trace would have the knowledge needed to know the incident trace has been completed by the existence of the Source Found message for that incident. Policies between NPs must be established to provide guidelines for communication. The policy should include communication methods, Moriarty Expires: April 21, 2005 [Page 57] Internet-Draft October 21, 2004 security, and fall-back procedures. The policy should establish a method to protect communications of RID systems between all bordering NPs. The trust relationships should extend to all bordering NPs to support tracing and stopping attacks throughout the network. A fully meshed communication ability would provide the means for Source Found messages to be sent directly to an initiating RID system. If a fully meshed communication system is not available, messages may have to traverse multiple systems to reach the initiating RID system. Other policy considerations include how the RegistryHandle and RID system IP address should be shared. This should also be coupled with any necessary pre-shared key or certificate (or trusted Security Authority) stored in the RID system for encryption negotiation, where PKI is in use. Note: The contact information and corresponding IP address for a network RID system is shared between cooperating networks via a predefined table. This information may be stored locally in RID systems or a central database accessible on the secured network used for inter-NP messaging. The repository can also be used as the border directory to other consortiums for sharing public key information necessary to establish and protect communications. The method of passing a Trace Request message to subsequent networks eliminates the need for granting access to remote entities to configure network equipment on border networks. Access to network equipment to configure systems for trace continuance remains in the responsibility of the parties who own and manage that equipment. Thus, there is no need to share authentication information with devices outside of the network operation center managing the device. Network administrators, who have the ability to base the decision on the available resources and other factors of their network, maintain control of the continuance of a trace. 8. Summary Security incidents and Denial of service attacks have always been difficult to trace as a result of the spoofed sources, resource limitations, and bandwidth utilization problems. Incident response is often slow even when the IP address is known to be valid because of the resources required to notify the responsible party of the attack and then to stop or mitigate the attack traffic. Methods to identify and trace attacks near real time are essential to thwarting attack attempts. Network providers need policies and automated methods combat the hacker's efforts. NPs need automated monitoring and response capabilities to identify and trace attacks quickly without resource intensive side effects. Integration with a centralized communication system to coordinate the detection, tracing, and identification of attack sources on a single network is essential. RID provides a way to integrate a network providers resources for each aspect of attack detection, tracing, and source identification and extends the communication capabilities between network providers. This is accomplished through the flexible IODEF Moriarty Expires: April 21, 2005 [Page 58] Internet-Draft October 21, 2004 XML based documents that may originate on an IDS system, which triggers a network trace. A Trace Request is communicated to an upstream provider and may result in an action to stop or mitigate the attack traffic. The messages are communicated between peers using the SOAP protocol and security considerations are provided through existing standards such as XML encryption and digital signatures. Policy information is carried in the RID message itself through the use of the RIDPolicy extension to the IODEF model. RID provides the timely communication between NPs, which is essential in incident handling. Moriarty Expires: April 21, 2005 [Page 59] Internet-Draft October 21, 2004 9. References [ISO 9594/8] CCITT Rec. X.509 (1994) | ISO/IEC 9594-8:1994, Information Technology - Open Systems Interconnection The Directory: Authentication Framework [RFC791] "Internet Protocol, DARPA Internet Program, Protocol Specification". Information Sciences Institute, University of Southern California. September 1981. [RFC1213] "Management Information Base for Network Management of TCP/IP-based Internets: MIB-II". K. McCloghrie, M . Rose. March 1991. [RFC1215] "A Convention for Defining Traps for use with the SNMP". M. Rose. March 1991. [RFC1930] "Guidelines for creation, selection, and registration of an Autonomous System (AS)". J. Hawkinson and T. Bates. March 1996. [RFC2246] "The TLS Protocol". Dierks, T. and C. Allen. January 1999. [RFC2256] "A Summary of the X.500(96) User Schema for use with LDAPv3", Wahl, M., December 1997. [RFC2459] "Internet Public Key Infrastructure: Part I: X.509 Certificate and CRL Profile". Housley, R., Ford, W., Polk, W. and D. Solo. January 1999. [RFC2527] "Internet X.509 Public Key Infrastructure: Certificate Policy and Certification Practices Framework". Chokhani, S., Ford, W. March 1999. [RFC2528] "Internet X.509 Public Key Infrastructure: Representation of Key Exchange Algorithm (KEA) Keys in Internet X.509 Public Key Infrastructure Certificates". Housley, R., Polk, W. March 1999. [RFC2720] "Traffic Flow Measurement: Meter MIB". N. Brownlee. October 1999. [RFC2722]"Traffic Flow Measurement: Architecture". N. Brownlee, C. Mills, G. Ruth. October 1999. [RFC2723] "SRL: A Language for Describing Traffic Flows and Specifying Actions for Flow Groups". N. Brownlee. October 1999. [RFC2827] "Network Ingress Filtering: Defeating Denial of Service Attacks Which Employ IP Source Address Spoofing". P. Ferguson and D. Senie. May 2000. Moriarty Expires: April 21, 2005 [Page 60] Internet-Draft October 21, 2004 [RFC3821] "An Internet Attribute Certificate Profile for Authorization". Farrell, S., Housley, R. April 2002. [RFCXXXX] ôThe Incident Data Exchange Format Data Model and XML Implementationö. J. Meijer, R. Danyliw, Y. Demchenko. September 2003. http://www.ietf.org/internet-drafts/draft-ietf-inch-iodef-02.txt [1] Advanced and Authenticated Marking Schemes for IP Traceback. D. Song and A. Perrig. IEEE INFOCOM 2001. [2] Applied Cryptography: Protocols, Algoritms, and Source Code in C. Schneier, Bruce. Second edition. John Wiley & Sons. 1996. [3] `CenterTrack: An IP Overlay Network for Tracing DoS Floods'. Robert Stone. 9th Usenix Security Symposium Proceedings, August 2000. [4] Extensible Markup Language (XML) 1.0 (Second Edition). W3C Recommendation. T. Bray, E. Maler, J. Paoli, C. M. Sperberg- McQueen. October 2000. http://www.w3.org/TR/2000/REC-xml-20001006 [5] http://www.cisco.com/go/netflow [6] http://www.info-sec.com/denial/infosece.html-ssi [7] 'Hash Based IP Traceback'. A. Snoren, L. Sanchez, C. Jones, F. Tchakountio, S. Kent, and W. Strayer. SIGCOMM'01. August 2001. [8] 'ICMP Traceback Messages'. S. M. Bellovin. Internet Draft: draft-bellovin-itrace-00.txt, March 2000. [9] 'Inferring Internet Denial of Service Activity`. David Moore, Geoffrey M. Voelker and Stephan Savage. Published in proceedings of the 2001 USENIX Security Symposium. [10] 'MULTOPS: A Data-Structure For Bandwidth Attack Detection'. Thomer M. Gil, Massimiliano Poletta. Published in proceedings of the 2001 USENIX Security Symposium. [11] 'Network Congestion Monitoring and Detection using the IMI infrastructure'. Takeo Saitoh, Glenn Mansfield, and Norio Shiratori. Graduate School of Information Sciences, Tohoku University. [12] PKCS 5 v2.0 Password-Based Cryptography Standard. RSA Security http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/index.html. March 1999. [13] PKCS 7 Cryptographic Message Syntax Standard. RSA Security. http://www.rsasecurity.com/rsalabs/pkcs/pkcs-7/index.html. Moriarty Expires: April 21, 2005 [Page 61] Internet-Draft October 21, 2004 May 1997. [14] 'Practical Network support for IP Traceback'. S.Savage, D. Wetherall, A. Karlin and T. Anderson. SIGCOMM'00. August 2000. [15] Security Architecture for Open Agent Systems. Vrije Universiteit. Y. Demchenko, B. Overiender, H. M. Boonstra. http://carol.science.uva.nl/~demch/worksinprogress/ draft-saas-paper03.pdf [16] Security in a Web Services World: A Proposed Architecture and Roadmapö. IBM and Microsoft. April 2002. http://www-106.ibm.com/developerworks/webservices/library/ws-secmap [17] SOAP Version 1.2 Part 0: Primer. W3C Recommendation. http://www.w3c.org/TR/REC-soap12-part0-20030624/. 24 June 2004. [18] SOAP Version 1.2 Part 1:Messaging Framework. W3C Recommendation. http://www.w3c.org/TR/REC-soap12-part1-20030624/. 24 June 2004. [19] 'Trends in Denial of Service Attack Technology`. Kevin Houle, George Weaver, Neil Long, and Rob Thomas. CERT Coordination Center. October 2001. [20] XML Encryption Syntax and Processing, W3C Recommendation. Imamura, T., Dillaway, B. and E. Simon, "", December 2002. http://www.w3.org/TR/xmlenc-core/ [21] XML Schema. Eric Van der Vlist. OÆReilly. 2002. [22] XML-Signature Syntax and Processing. W3C Recommendation. M. Bartel, J. Boyer, B. Fox, B. LaMacchia , E. Simon. February 2002. http://www.w3.org/TR/xmldsig-core/#sec-Design Moriarty Expires: April 21, 2005 [Page 62] Internet-Draft October 21, 2004 9.1 Acknowledgements Many thanks to coworkers and the Internet community for reviewing and commenting on the draft as well as providing recommendations to simplify and secure the protocol: Dr. Robert K. Cunningham, Cynthia D. McLain, Dr. William Streilein, Iljitsch van Beijnum, Steve Bellovin, Yuri Demchenko, Jean-Francois Morfin, Jose Nazaro, Stephen Northcutt, Jeffrey Schiller, and Tony Tauber. 9.2 Author Information Kathleen M. Moriarty MIT Lincoln Laboratory 244 Wood Street Lexington, MA 02420 Phone: 781-981-5500 Email: Moriarty@ll.mit.edu Copyright (C) The Internet Society 2004. This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION SHE REPRESENTS IS SPONSORED BY THE AIR FORCE, THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. This work was sponsored by the Air Force under Air Force Contract Number F19628-00-C-0002. "Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Government." Moriarty Expires: April 21, 2005 [Page 63]