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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force Tom Killalea 2 INTERNET-DRAFT neart.org 3 Valid for six months July 2000 5 Security Expectations for Internet Service Providers 7 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of RFC2026. Internet Drafts are working 13 documents of the Internet Engineering Task Force (IETF), its Areas, 14 and its Working Groups. Note that other groups may also distribute 15 working documents as Internet Drafts. 17 Internet Drafts are draft documents valid for a maximum of six 18 months. Internet Drafts may be updated, replaced, or obsoleted by 19 other documents at any time. It is inappropriate to use Internet 20 Drafts as reference material or to cite them other than as "work in 21 progress." 23 The list of current Internet-Drafts can be accessed at 24 http://www.ietf.org/ietf/1id-abstracts.txt 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 Copyright Notice 31 Copyright (C) The Internet Society (2000). All Rights Reserved. 33 Abstract 35 The purpose of this document is to express the general Internet 36 community's expectations of Internet Service Providers (ISPs) with 37 respect to security. 39 It is not the intent of this document to define a set of requirements 40 that would be appropriate for all ISPs, but rather to raise awareness 41 among ISPs of the community's expectations, and to provide the 42 community with a framework for discussion of security expectations 43 with current and prospective service providers. 45 Table of Contents 46 1 Introduction 47 1.1 Conventions Used in this Document 49 2 Communication 50 2.1 Contact Information 51 2.2 Information Sharing 52 2.3 Secure Channels 53 2.4 Notification of Vulnerabilities and Reporting Incidents 54 2.5 ISPs and Computer Security Incident Response Teams (CSIRTs) 56 3 Appropriate Use Policy 57 3.1 Announcement of Policy 58 3.2 Sanctions 59 3.3 Data Protection 61 4 Network Infrastructure 62 4.1 Registry Data Maintenance 63 4.2 Routing Infrastructure 64 4.3 Ingress Filtering on Source Address 65 4.4 Egress Filtering on Source Address 66 4.5 Route Filtering 67 4.6 Directed Broadcast 69 5 Systems Infrastructure 70 5.1 System Management 71 5.2 No Systems on Transit Networks 72 5.3 Open Mail Relay 73 5.4 Message Submission 75 6 References 77 7 Acknowledgements 79 8 Security Considerations 81 9 Author's Address 83 10 Full Copyright Statement 85 1 Introduction 87 The purpose of this document is to express the general Internet 88 community's expectations of Internet Service Providers (ISPs) with 89 respect to security. This document is addressed to ISPs. 91 By informing ISPs of what the community hopes and expects of them, 92 the community hopes to encourage ISPs to become proactive in making 93 security not only a priority, but something to which they point with 94 pride when selling their services. 96 Under no circumstances is it the intention of this document to 97 dictate business practices. 99 In this document we define ISPs to include organisations in the 100 business of providing Internet connectivity or other Internet 101 services including but not restricted to web hosting services, 102 content providers and e-mail services. We do not include in our 103 definition of an ISP organisations providing those services for their 104 own purposes. 106 1.1 Conventions Used in this Document 108 The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", 109 and "MAY" in this document are to be interpreted as described in "Key 110 words for use in RFCs to Indicate Requirement Levels" [RFC2119]. 112 2 Communication 114 The community's most significant security-related expectations of 115 ISPs relate to the availability of communication channels for dealing 116 with security incidents. 118 2.1 Contact Information 120 ISPs SHOULD adhere to [RFC2142], which defines the mailbox SECURITY 121 for network security issues, ABUSE for issues relating to 122 inappropriate public behaviour and NOC for issues relating to network 123 infrastructure. It also lists additional mailboxes that are defined 124 for receiving queries and reports relating to specific services. 126 ISPs may consider using common URLs for expanded details on the above 127 (e.g., http://www.ISP-name-here.net/security/). 129 In addition, ISPs have a duty to make sure that their contact 130 information, in Whois, in routing registries [RFC1786] or in any 131 other repository, is complete, accurate and reachable. 133 2.2 Information Sharing 135 ISPs SHOULD have clear policies and procedures on the sharing of 136 information about a security incident with their customers, with 137 other ISPs, with Incident Response Teams, with law enforcement or 138 with the press and general public. 140 ISPs should have processes in place to deal with security incidents 141 that traverse the boundaries between them and other ISPs. 143 2.3 Secure Channels 145 ISPs SHOULD be able to conduct such communication over a secure 146 channel. Note, however, that in some jurisdictions secure channels 147 might not be permitted. 149 2.4 Notification of Vulnerabilities and Reporting of Incidents 151 ISPs SHOULD be proactive in notifying customers of security 152 vulnerabilities in the services they provide. In addition, as new 153 vulnerabilities in systems and software are discovered they should 154 indicate whether their services are threatened by these risks. 156 When security incidents occur that affect components of an ISP's 157 infrastructure the ISP should promptly report to their customers 159 - who is coordinating response to the incident 161 - the vulnerability 163 - how service was affected 165 - what is being done to respond to the incident 167 - whether customer data may have been compromised 169 - what is being done to eliminate the vulnerability 171 - the expected schedule for response, assuming it can be 172 predicted 174 Many ISPs have established procedures for notifying customers of 175 outages and service degradation. It is reasonable for the ISP to use 176 these channels for reporting security-related incidents. In such 177 cases, the customer's security point of contact might not be the 178 person notified. Rather, the normal point of contact will receive 179 the report. Customers should be aware of this and make sure to route 180 such notifications appropriately. 182 2.5 Incident Response and Computer Security Incident Response Teams 183 (CSIRTs) 185 A Computer Security Incident Response Team (CSIRT) is a team that 186 performs, coordinates, and supports the response to security 187 incidents that involve sites within a defined constituency. The 188 Internet community's expectations of CSIRTs are described in 189 "Expectations for Computer Security Incident Response" [RFC2350]. 191 Whether or not an ISP has a CSIRT, they should have a well-advertised 192 way to receive and handle reported incidents from their customers. 193 In addition, they should clearly document their capability to respond 194 to reported incidents, and should indicate if there is any CSIRT 195 whose constituency would include the customer and to whom incidents 196 could be reported. 198 Some ISPs have CSIRTs. However it should not be assumed that either 199 the ISP's connectivity customers or a site being attacked by a 200 customer of that ISP can automatically avail themselves of the 201 services of the ISP's CSIRT. ISP CSIRTs are frequently provided as 202 an added-cost service, with the team defining as their constituency 203 only those who specifically subscribe to (and perhaps pay for) 204 Incident Response services. 206 Thus it's important for ISPs to publish what incident response and 207 security resources they make available to customers, so that the 208 customers can define their incident response escalation chain BEFORE 209 an incident occurs. 211 Customers should find out whether their ISP has a CSIRT, and if so 212 what the charter, policies and services of that team are. This 213 information is best expressed using the CSIRT template as shown in 214 Appendix D of "Expectations for Computer Security Incident Response" 215 [RFC2350]. 217 3 Appropriate Use Policy 219 Every ISP SHOULD have an Appropriate Use Policy (AUP). 221 Whenever an ISP contracts with a customer to provide connectivity to 222 the Internet that contract should be governed by an AUP. The AUP 223 should be reviewed each time the contract is up for renewal, and in 224 addition the ISP should proactively notify customers as policies are 225 updated. 227 An AUP should clearly identify what customers shall and shall not do 228 on the various components of a system or network, including the type 229 of traffic allowed on the networks. The AUP should be as explicit as 230 possible to avoid ambiguity or misunderstanding. For example, an AUP 231 might prohibit IP spoofing. 233 3.1 Announcement of Policy 235 In addition to communicating their AUP to their customers ISPs should 236 publish their policy in a public place such as their web site so that 237 the community can be aware of what the ISP considers appropriate and 238 can know what action to expect in the event of inappropriate 239 behaviour. 241 3.2 Sanctions 243 An AUP should be clear in stating what sanctions will be enforced in 244 the event of inappropriate behaviour. 246 3.3 Data Protection 248 Many jurisdictions have Data Protection Legislation. Where such 249 legislation applies, ISPs should consider the personal data they hold 250 and, if necessary, register themselves as Data Controllers and be 251 prepared to only use the data in accordance with the terms of the 252 legislation. Given the global nature of the Internet ISPs that are 253 located where no such legislation exists should at least familiarise 254 themselves with the idea of Data Protection by reading a typical Data 255 Protection Act (e.g., [DPR1998]). 257 4 Network Infrastructure 259 ISPs are responsible for managing the network infrastructure of the 260 Internet in such a way that it is 262 - reasonably resistant to known security vulnerabilities 264 - not easily hijacked by attackers for use in subsequent attacks 266 4.1 Registry Data Maintenance 268 ISPs are commonly responsible for maintaining the data that is stored 269 in global repositories such as the Internet Routing Registry (IRR) 270 and the APNIC, ARIN and RIPE databases. Updates to this data should 271 only be possible using strong authentication. 273 ISPs should publicly register the address space that they assign to 274 their customers so that there is more specific contact information 275 for the delegated space. 277 4.2 Routing Infrastructure 279 An ISP's ability to route traffic to the correct destination may 280 depend on routing policy as configured in routing registries 281 [RFC1786]. If so, and if the registry supports it, they should 282 ensure that the registry information that they maintain can only be 283 updated using strong authentication, and that the authority to make 284 updates is appropriately restricted. 286 Due care should also be taken in determining in whose routing 287 announcements you place greater trust when a choice of routes are 288 available to a destination. In the past bogus announcements have 289 resulted in traffic being 'black holed', or worse, hijacked. 291 BGP authentication [RFC2385] should be used with routing peers. 293 4.3 Ingress Filtering on Source Address 295 The direction of such filtering is from the edge site (customer) to 296 the Internet. 298 Attackers frequently cover their tracks by using forged source 299 addresses. To divert attention from their own site the source 300 address they choose will generally be from an innocent remote site or 301 indeed from those addresses that are allocated for private Internets 302 [RFC1918]. In addition, forged source addresses are frequently used 303 in spoof-based attacks in order to exploit a trust relationship 304 between hosts. 306 To reduce the incidence of attacks that rely on forged source 307 addresses ISPs should do the following. At the boundary router with 308 each of their customers they should proactively filter all traffic 309 coming from the customer that has a source address of something other 310 than the addresses that have been assigned to that customer. For a 311 more detailed discussion of this topic see [RFC2267]. 313 There are (rare) circumstances where ingress filtering is not 314 currently possible, for example on large aggregation routers that 315 cannot take the additional load of applying packet filters. In 316 addition, such filtering can cause difficulty for mobile users. 317 Hence, while the use of this technique to prevent spoofing is 318 strongly encouraged, it may not always be feasible. 320 In these rare cases where ingress filtering at the interface between 321 the customer and the ISP is not possible, the customer should be 322 encouraged to implement ingress filtering within their networks. In 323 general filtering should be done as close to the actual hosts as 324 possible. 326 4.4 Egress Filtering on Source Address 328 The direction of such filtering is from the Internet to the edge site 329 (customer). 331 There are many applications in widespread use on the Internet today 332 that grant trust to other hosts based only on ip address (e.g., the 333 Berkeley 'r' commands). These are susceptible to IP spoofing, as 334 described in [CA-95.01.IP.spoofing]. In addition, there are 335 vulnerabilities that depend on the misuse of supposedly local 336 addresses, such as 'land' as described in [CA-97.28.Teardrop_Land]. 338 To reduce the exposure of their customers to attacks that rely on 339 forged source addresses ISPs should do the following. At the 340 boundary router with each of their customers they should proactively 341 filter all traffic going to the customer that has a source address of 342 any of the addresses that have been assigned to that customer. 344 The circumstances described in 4.3 in which ingress filtering isn't 345 feasible apply similarly to egress filtering. 347 4.5 Route Filtering 349 Excessive routing updates can be leveraged by an attacker as a base 350 load on which to build a Denial of Service attack. At the very least 351 they will result in performance degradation. 353 ISPs should filter the routing announcements they hear, for example 354 to ignore routes to addresses allocated for private Internets, to 355 avoid bogus routes and to implement "BGP Route Flap Dampening" 356 [RFC2439] and aggregation policy. 358 ISPs should implement techniques that reduce the risk of putting 359 excessive load on routing in other parts of the network. These 360 include 'nailed up' routes, aggressive aggregation and route 361 dampening, all of which lower the impact on others when your internal 362 routing changes in a way that isn't relevant to them. 364 4.6 Directed Broadcast 365 The IP protocol allows for directed broadcast, the sending of a 366 packet across the network to be broadcast on to a specific subnet. 367 Very few practical uses for this feature exist, but several different 368 security attacks (primarily Denial of Service attacks making use of 369 the packet multiplication effect of the broadcast) use it. 370 Therefore, routers connected to a broadcast medium MUST NOT be 371 configured to allow directed broadcasts onto that medium [RFC2644]. 373 5 Systems Infrastructure 375 The way an ISP manages their systems is crucial to the security and 376 reliability of their network. A breach of their systems may 377 minimally lead to degraded performance or functionality, but could 378 lead to loss of data or the risk of traffic being eavesdropped (thus 379 leading to 'man-in-the-middle' attacks). 381 It's widely accepted that it's easier to build secure systems if 382 different services (such as mail, news and web-hosting) are kept on 383 separate systems. 385 5.1 System Management 387 All systems that perform critical ISP functions such as mail, news 388 and web-hosting, should be restricted such that access to them is 389 only available to the administrators of those services. That access 390 should be granted only following strong authentication, and should 391 take place over an encrypted link. Only the ports on which those 392 services listen should be reachable from outside of the ISP's systems 393 networks. 395 ISPs should stay up to date for more secure methods of providing 396 services as they become available (e.g., IMAP/POP AUTHorize Extension 397 for Simple Challenge/Response, [RFC2195]). 399 5.2 No Systems on Transit Networks 401 Systems should not be attached to transit network segments. 403 5.3 Open Mail Relay 405 An SMTP mail server is said to be running as an 'open' mail relay if 406 it is willing to accept and relay to non-local destinations mail 407 messages that do not originate locally (i.e., neither the originator 408 nor the recipient address is local). Such open relays are frequently 409 used by 'spammers' to inject their Unsolicited Bulk E-mail (UBE) 410 while hiding their identity [RFC2505]. There are only very limited 411 circumstances in which an administrator can make a justifiable case 412 for leaving a mail relay on the Internet completely open. 414 The processes for restricting relaying are well documented. It's 415 regrettable that some major software vendors ship their Message 416 Transfer Agents (MTAs) with relaying open by default. 418 While this is an issue for the whole community, ISPs should be 419 particularly vigilant in disabling open relaying on mail servers that 420 they manage because their high-bandwidth connectivity makes them the 421 preferred injection point for UBE. 423 ISPs should also strongly encourage their customers to disable open 424 relaying on their mail servers. 426 5.4 Message Submission 428 Message submissions should be authenticated using the AUTH SMTP 429 service extension as described in the "SMTP Service Extension for 430 Authentication" [RFC2554]. 432 SMTP AUTH is preferred over IP address-based submission restrictions 433 in that it gives the ISP's customers the flexibility of being able to 434 submit mail even when not connected through the ISP's network (for 435 example, while at work), is more resistant to spoofing, and can be 436 upgraded to newer authentication mechanisms as they become available. 438 In addition, to facilitate the enforcement of security policy, it is 439 strongly recommended that messages be submitted using the MAIL SUBMIT 440 port (587) as discussed in "Message Submission" [RFC2476], rather 441 than through the SMTP port (25). In this way the SMTP port (25) can 442 be restricted to local delivery only. 444 The reason for this is to be able to differentiate between inbound 445 local delivery and relay (i.e., allow customers to send email via the 446 ISP's SMTP service to arbitrary receivers on the Internet). Non- 447 authenticated SMTP should only be allowed for local delivery. 449 As more and more mail clients support both SMTP AUTH and the message 450 submission port (either explicitly or by configuring the SMTP port), 451 ISPs may find it useful to require that customers submit messages 452 using both the submission port and SMTP AUTH; permitting only inbound 453 mail on port 25. 455 These measures (SMTP AUTH and the submission port) not only protect 456 the ISP from serving as a UBE injection point via third-party relay, 457 but also help in tracking accountability for message submission in 458 the case where a customer sends UBE. 460 6 References 462 [CA-95.01.IP.spoofing] "IP Spoofing Attacks and Hijacked Terminal 463 Connections", ftp://info.cert.org/pub/cert_advisories/ 465 [CA-97.28.Teardrop_Land] "IP Denial-of-Service Attacks", 466 ftp://info.cert.org/pub/cert_advisories/ 468 [DPR1998] The UK "Data Protection Act 1998 (c. 29)", 469 http://www.hmso.gov.uk/acts/acts1998/19980029.htm 471 [RFC1786] Bates, T., Gerich, E., Joncheray, L., Jouanigot, J-M., 472 Karrenberg, D., Terpstra, M., and J. Yu, "Representation of IP 473 Routing Policies in a Routing Registry (ripe-81++)", RFC 1786, 474 March 1995. 476 [RFC1834] Gargano, J., and K. Weiss, "Whois and Network Information 477 Lookup Service", RFC 1834, August 1995. 479 [RFC1835] Deutsch, P., Schoultz, R., Faltstrom, P., and C. Weider, 480 "Architecture of the WHOIS++ service", RFC 1835, August 1995. 482 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. 483 J., and E. Lear, "Address Allocation for Private Internets", BCP 5, 484 RFC 1918, February 1996. 486 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 487 Requirement Levels", RFC 2119, March 1997. 489 [RFC2142] Crocker, D., "Mailbox Names for Common Services, Roles and 490 Functions", RFC 2142, May 1997. 492 [RFC2195] Klensin, J., Catoe, R., and P. Krumviede, "IMAP/POP 493 AUTHorize Extension for Simple Challenge/Response", RFC 2195, 494 September 1997. 496 [RFC2196] Fraser, B., "Site Security Handbook", RFC 2196, September 497 1997. 499 [RFC2267] Ferguson, P., and D. Senie, "Network Ingress Filtering: 500 Defeating Denial of Service Attacks which employ IP Source 501 Address Spoofing", RFC 2267, January 1998. 503 [RFC2350] Brownlee, N., and E. Guttman, "Expectations for Computer 504 Security Incident Response", RFC 2350, June 1998. 506 [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 507 Signature Option", RFC 2385, August 1998. 509 [RFC2439] Chandra R., Govindan R., and C. Villamizar, "BGP Route 510 Flap Damping", RFC 2439, November 1998. 512 [RFC2476] Gellens R., and J. Klensin, "Message Submission", 513 RFC 2476, December 1998. 515 [RFC2505] Lindberg, G., "Anti-Spam Recommendations for SMTP MTAs", 516 RFC 2505, February 1999. 518 [RFC2554] Myers, J., "SMTP Service Extension for Authentication", 519 RFC 2554, March 1999. 521 [RFC2644] 522 Senie, D., "Changing the Default for Directed Broadcasts in 523 Routers", RFC 2644, August 1999. 525 7 Acknowledgements 527 I gratefully acknowledge the constructive comments received from 528 Nevil Brownlee, Randy Bush, Bill Cheswick, Barbara Y. Fraser, Randall 529 Gellens, Erik Guttman, Larry J. Hughes Jr., Klaus-Peter Kossakowski, 530 Michael A. Patton, Don Stikvoort and Bill Woodcock. 532 8 Security Considerations 534 This entire document discusses security issues. 536 9 Author's Address 538 Tom Killalea 539 P.O. Box 81226 540 Seattle, WA 98108-1226 541 USA 543 Phone: +1 206 266-2196 544 E-Mail: tomk@neart.org 546 10 Full Copyright Statement 547 Copyright (C) The Internet Society (2000). All Rights Reserved. 549 This document and translations of it may be copied and furnished to 550 others, and derivative works that comment on or otherwise explain it 551 or assist in its implmentation may be prepared, copied, published and 552 distributed, in whole or in part, without restriction of any kind, 553 provided that the above copyright notice and this paragraph are 554 included on all such copies and derivative works. However, this 555 document itself may not be modified in any way, such as by removing 556 the copyright notice or references to the Internet Society or other 557 Internet organisations, except as needed for the purpose of 558 developing Internet standards in which case the procedures for 559 copyrights defined in the Internet Standards process must be 560 followed, or as required to translate it into languages other than 561 English. 563 The limited permissions granted above are perpetual and will not be 564 revoked by the Internet Society or its successors or assigns. 566 This document and the information contained herein is provided on an 567 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 568 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 569 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 570 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 571 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." 573 This document expires Jan 9, 2001.