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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force J. Livingood 3 Internet-Draft N. Mody 4 Intended status: Informational M. O'Reirdan 5 Expires: February 27, 2010 Comcast 6 August 26, 2009 8 Recommendations for the Remediation of Bots in Large ISP Networks 9 draft-oreirdan-mody-bot-remediation-01 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. This document may contain material 15 from IETF Documents or IETF Contributions published or made publicly 16 available before November 10, 2008. The person(s) controlling the 17 copyright in some of this material may not have granted the IETF 18 Trust the right to allow modifications of such material outside the 19 IETF Standards Process. Without obtaining an adequate license from 20 the person(s) controlling the copyright in such materials, this 21 document may not be modified outside the IETF Standards Process, and 22 derivative works of it may not be created outside the IETF Standards 23 Process, except to format it for publication as an RFC or to 24 translate it into languages other than English. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF), its areas, and its working groups. Note that 28 other groups may also distribute working documents as Internet- 29 Drafts. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 The list of current Internet-Drafts can be accessed at 37 http://www.ietf.org/ietf/1id-abstracts.txt. 39 The list of Internet-Draft Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 This Internet-Draft will expire on February 27, 2010. 44 Copyright Notice 46 Copyright (c) 2009 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents in effect on the date of 51 publication of this document (http://trustee.ietf.org/license-info). 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. 55 Abstract 57 This document contains recommendations on how large Internet Service 58 Providers (ISPs) can manage the effects of large numbers of bot 59 infected computers used by their subscribers via various remediation 60 techniques. At the time that this document was published, computers 61 infected by bots and the users of those computers comprise a 62 substantial number of users for large ISPs. Those Internet users are 63 exposed to risks such as loss of personal data, increased 64 susceptibility to online fraud and/or phishing, and becoming an 65 inadvertent participant in or component of an online crime, spam, 66 and/or phishing network. Mitigating the effects of and remediating 67 the installations of bots affecting large numbers of Internet users 68 will make it more difficult for botnets to operate and could reduce 69 the level of online crime on the Internet in general and/or on a 70 particular ISP's network. 72 Table of Contents 74 1. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 75 2. Key Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 76 3. Introduction and Problem Statement . . . . . . . . . . . . . . 5 77 4. Important Notice of Limitations . . . . . . . . . . . . . . . 7 78 5. Detection, Notification and Remediation . . . . . . . . . . . 7 79 5.1. Detection of Bots . . . . . . . . . . . . . . . . . . . . 7 80 5.2. Notification to Internet Users . . . . . . . . . . . . . . 11 81 5.3. Remediation of Bot Infected Machines . . . . . . . . . . . 15 82 5.4. Guided Remediation Process . . . . . . . . . . . . . . . . 16 83 6. Security Considerations . . . . . . . . . . . . . . . . . . . 17 84 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 85 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 86 9. Informative references . . . . . . . . . . . . . . . . . . . . 18 87 Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 18 88 Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 19 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 91 1. Requirements Language 93 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 94 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 95 document are to be interpreted as described in [RFC2119]. 97 2. Key Terminology 99 This section defines the key terms used in this document. 101 2.1. Bots 103 A "bot" (derived from the word "robot") refers to a program that is 104 surreptitiously installed on a system in order to enable that system 105 to automatically (or semi-automatically) perform a task or set of 106 tasks typically under the command and control of a remote 107 administrator, or "bot master." Bots are also known as "zombies." 108 It is important to note that there are 'good' bots. Such benign bots 109 are often found in such environments such as gaming and Internet 110 Relay Chat (IRC) [RFC1459], where a continual, interactive presence 111 can be a requirement for participating in the games, interacting with 112 a computing resource, or other purposes. However, for the purposes 113 of this document, all mention of bots should assume that the bots 114 involved are malicious in nature. Such malicious bots shall 115 generally be assumed to have been deployed without the permission or 116 conscious understanding of a particular Internet user. Thus, without 117 a user's knowledge, bots may transform the user's computing device 118 into a platform from which malicious activities are conducted. 120 2.2. Bot Networks, or Botnets 122 These are defined as concerted networks of bots capable of acting on 123 instructions generated remotely. The malicious activities are either 124 focused on the information on the local machine or acting to provide 125 services for remote machines. Bots are highly customizable so they 126 can be programmed to do many things. The major malicious activities 127 include: identity theft, spam, denial of service attacks, key- 128 logging, fraudulent DNS (pharming), proxy services, fast flux hosting 129 and click fraud. Infection vectors include un-patched operating 130 systems, software vulnerabilities, weak/non-existent passwords, 131 malicious websites, un-patched browsers, malware, vulnerable helper 132 applications and social engineering techniques to gain access to the 133 user's computer. The detection and destruction of bots is an ongoing 134 issue and also a constant battle between the internet security 135 community, network security engineers and bot developers. Initially 136 bots used IRC to communicate but were easy to shutdown if the command 137 and control server was identified and deactivated. However, newer 138 command and control topologies employed by bot masters make them much 139 more resistant to deactivation. With the introduction of P2P, HTTP 140 and other resilient communication protocols along with the widespread 141 adoption of encryption, bots are considerably more difficult to 142 identify and isolate from typical network usage. As a result 143 increased reliance is being placed on anonmaly detection and 144 behavioral analysis, both locally and remotely, to identify bots. 146 2.3. Computer 148 A computer, as used in the context of this document, is intended to 149 encompass the computing devices networked and reliant upon the 150 Internet for communications, software updates and functional 151 operation. This encompasses devices used directly by Internet users 152 such as personal computers, including laptops, desktops, and 153 netbooks, as well as mobile phones, smart phones, home gateway 154 devices, and other end user computing devices which are connected or 155 can connect to the public Internet and/or private IP networks. 157 Increasingly, other household systems and devices contain embedded 158 computers which are connected or can connect to the public Internet 159 and/or private IP networks. However, these devices may not be under 160 interactive control of the Internet user. Smart home technologies 161 that manage energy consumption and monitor household appliances or 162 environments have become more common and are more often networked. 163 This is with or without the homeowners knowledge or ability to alter 164 functionality. 166 2.4. Malware 168 This is short for "malicious software." In this case, malicious bots 169 are considered a subset of malware, which could also include viruses 170 and other similar types of software. Internet users can sometimes 171 cause their computer to be infected with malware, which may include a 172 bot or cause a bot to install itself, via inadvertently accessing a 173 specific website, downloading a specific file, or other activities. 175 Alternatively, Internet accessible devices may become infected with 176 malware through externally initiated malicious activities such as the 177 exploitation of vulnerabilities or the brute forced guessing of 178 access credentials. 180 3. Introduction and Problem Statement 182 Computers used by Internet users, which in this case are customers of 183 an Internet Service Provider (ISP), can be infected with malware 184 which may contain and/or install one or more bots on a computer. 186 This can present a major problem for an ISP for a number of reasons 187 (not to mention of course the problems created for users). First, 188 these bots can be used to send spam, in some cases very large volumes 189 of spam. This spam can result in extra cost for the ISPs in terms of 190 wasted network, server, and/or personnel resources, among many other 191 potential costs or side effects. Such spam can also negatively 192 affect the reputation of the ISP, their customers, and the email 193 reputation of the IP address space used by the ISP (often referred to 194 simply as "IP reputation"). 196 In addition, these bots can act as platforms for directing, 197 participating in, or otherwise conducting attacks on critical 198 Internet infrastructure. Bots are frequently used as part of 199 concerted Distributed Denial of Service (DDoS) attacks for criminal, 200 political or other motivations. For example, bots have been used to 201 attack Internet resources and infrastructure ranging from web sites, 202 to email servers and DNS servers, as well as the critical Internet 203 infrastructure of entire countries. Motivations for such coordinated 204 DDoS attacks can range from criminal extortion attempts through to 205 online protesting and nationalistic fervor. 207 While any computing device can be infected with bots, the majority of 208 bot infections affect the personal computers used by Internet end 209 users. As a result of the role of ISPs in providing IP connectivity, 210 among many other services, to Internet users, these ISPs are in a 211 unique position to be able to attempt to detect and observe bot nets 212 operating in their networks. Furthermore, ISPs may also be in a 213 unique position to be able to communicate to Internet users which are 214 their customers, when customers computers may have been determined to 215 have been or possibly have been infected with one or more bots. 217 From an end user perspective, knowing that their computer has been 218 infected with one or more bots is very important information. Once 219 they know this, they can take steps to remove the bot, protect 220 themselves in the future, and resolve any problems which may stem 221 from the bot infection. Given that bots can drain the local 222 computing and network resources, enable theft of personal information 223 (including personal financial information), enable the computer to be 224 used from criminal activities (that may result in the Internet user 225 being legally culpable), destroy or leave the PC in an unrecoverable 226 state via 'kill switch' bot technologies, it is important to notify 227 the user that they may be infected with a bot. 229 As a result, the intent of this document is to provide a guide to 230 ISPs and other organizations for the remediation of these computers 231 infected with bots, so as to reduce the size of bot nets and minimize 232 the potential harm that bots can inflict upon Internet infrastructure 233 generally, as well as on individual Internet users. Efforts by ISPs 234 and other organizations could therefore, over time, reduce the pool 235 of computers infected with bots on the Internet, which in turn could 236 result in smaller bot nets with less capability for disruption. 238 4. Important Notice of Limitations 240 The techniques described in this document in no way guarantee the 241 remediation of all bots. Bot removal is potentially a task requiring 242 specialized knowledge, skills and tools, and may be beyond the 243 ability of average users. Attempts at bot removal may frequently be 244 unsuccessful, or only partially successful, and may leave a user's 245 system in an unstable and unsatisfactory state or even still 246 infected. Attempts at bot removal can also result in side effects 247 ranging from a loss of data or other files, all the way through 248 partial or complete loss of system usability. 250 In general, the only way a user can be sure they have removed some of 251 today's increasingly sophisticated malware is by "nuking-and-paving" 252 the system: reformatting the drive, reinstalling the operating system 253 and applications (including all patches) from scratch, and then 254 restoring user files from a clean backup. However the introduction 255 of BIOS based malware may mean that in some cases, this will not be 256 enough and may prove to be more than any end user can be reasonably 257 expected to resolve. 259 Devices with embedded operating systems, such as video gaming 260 consoles and smart home appliances, will most likely be beyond a 261 user's capability to remediate by themselves, and will typically 262 require the aid of vendor specific advice, updates and tools. Care 263 must be taken when imparting remediation advice to Internet users 264 given the increasingly wide array of computing devices that can be, 265 or could be, bot infected in the future. 267 5. Detection, Notification and Remediation 269 The potential mitigation of bots is accomplished through a process of 270 detection, notification to Internet users, and remediation of that 271 bot with a variety of tools. 273 5.1. Detection of Bots 275 An ISP must first identify that an Internet user, in this case a user 276 that is assumed to be their customer or otherwise connected to the 277 ISP's network, is determined to be infected, or likely to have been 278 infected with a bot. The ISP should attempt to detect the presence 279 of bots using methods, processes, and tools which maintain the 280 privacy of the personally identifiable information of their 281 customers. The ISP also should not block legitimate traffic in the 282 course of bot detection, and should instead employ detection methods, 283 tools, and processes which seek to be non-disruptive, as well as 284 being transparent to Internet users. 286 Detection methods, tools, and processes may include things such as 287 analysis of specific network and/or application traffic flows (such 288 as traffic to an email server), analysis of aggregate network and/or 289 application traffic data, data feeds received from other ISPs and 290 organizations (such as lists of the ISP's IP addresses which have 291 been reported to have sent spam), feedback from the ISP's customers 292 or other Internet users, as well as a wide variety of other 293 possibilities. It is likely that a combination of multiple bot 294 detection data points will prove to be an effective approach in order 295 to corroborate information of varying dependability or consistency, 296 as well as to avoid or minimize the possibility of false positive 297 identification of computers. Detection should also, where possible 298 and feasible, attempt to classify a bot in order to confirm that it 299 is malicious in nature, estimate the variety and severity of threats 300 it may pose (such as spam bot, key-logging bot, file distribution 301 bot, etc.), and to determine potential methods for eventual 302 remediation. However, given the dynamic nature of botnet management 303 and the criminal incentives to seek quick financial rewards, botnets 304 frequently update or change their core malicious capabilities. As a 305 consequence, botnets that are initially detected and classified by 306 the ISP need to be continuously monitored and tracked in order to 307 correctly identify the threat they pose at any particular point in 308 time. 310 Detection is also time-sensitive. If complex analysis is required 311 and multiple confirmations are needed to confirm a bot is indeed 312 present, then it is possible that the bot will do its damage (to 313 either the infected computer or a remotely targeted system) before it 314 can be stopped. This may mean that an ISP may need to balance the 315 desire or need to definitively classify and/or confirm a bot, which 316 may take an extended period of time, with the ability to predict the 317 strong likelihood of a bot in a very short period of time. This also 318 means that Internet users may benefit from the deployment of client- 319 based software protections or other software tools, which can enable 320 rapid performance of heuristically-based detection bot activity, such 321 as the detection of a bot as it starts to communicate a bot net and 322 execute some type of command. Any bot detection systems should also 323 be capable of learning and adapting, either via manual intervention 324 or automatically, in order to cope with a rapidly evolving threat. 326 As noted above, detection methods, tools, and processes should ensure 327 that privacy of customers' personally identifiable information is 328 maintained. While bot detection methods, tools, and processes are 329 similar to spam and virus defenses deployed by the ISP for the 330 benefits of their customers (and may be directly related to those 331 defenses), attempts to detect bots should take into account the need 332 of an ISP to take care to ensure that such personally identifiable 333 information is properly protected. Finally, depending upon the 334 geographic region within which an ISP operates, certain methods 335 relating to bot detection may need to be included in relevant terms 336 of service documents or other documents which are available to the 337 customers of a particular ISP. 339 There are several bot detection methods, tools, and processes that an 340 ISP may choose to utilize, as noted in the list below. It is 341 important to note that the technical solutions available are 342 relatively immature, and are likely to change over time, and to 343 evolve rapidly in the coming years. While these items are described 344 in relation to ISPs, they may also be applicable to organizations 345 operating other networks, such as campus networks and enterprise 346 networks. 348 a. Where legally permissible or otherwise an industry accepted 349 practice in a particular market region, an ISP may in some manner 350 "scan" their IP space in order to detect un-patched or otherwise 351 vulnerable hosts. This may provide the ISP with the opportunity 352 to easily identify Internet users who appear to already be or are 353 at great risk of being infected with a bot. ISP's should note 354 that some types of port scanning may leave network services in a 355 hung state or render them unusable due to common frailties, and 356 that many modern firewall and host-based intrusion detection 357 implementations may alert the Internet user to the scan. As a 358 result the scan may be interpreted as a malicious attack against 359 the computer. Vulnerability scanning has a higher probability of 360 leaving accessible network services and applications in a damaged 361 state and will often result in a higher probability of detection 362 by the Internet user and subsequent interpretation as a targeted 363 attack. Depending upon the vulnerability being scanned, some 364 automated methods of vulnerability checking may result in data 365 being altered or created afresh on the Internet users computer 366 which be a problem in many legal environments. 368 b. An ISP may also communicate and share selected data, via feedback 369 loops or other mechanisms, with various third parties. Feedback 370 loops are consistently formatted feeds of real-time (or nearly 371 real-time) abuse reports offered by threat data clearinghouses, 372 security alert organizations, other ISPs, and other 373 organizations. The data may include, but is not limited to, 374 lists of the IP addresses computers which have or are likely to 375 have a bot running, domain names or fully qualified domain names 376 (FQDNs) known to host malware and/or be involved in the command 377 and control of botnets, IP addresses know to host malware and/or 378 be involved in the command and control of botnets, recently 379 tested or discovered techniques or detecting or remediating bot 380 infections, new threat vectors, and other relevant information. 381 Good examples of this include SNDS from Microsoft, XBL and PBL 382 from Spamhaus and DSHIELD AS tool from SANS 384 c. An ISP may use Netflow [RFC3954] or other similar passive network 385 monitoring to identify network anomalies that may be indicative 386 of botnet attacks or bot communications. For example, an ISP may 387 be able to identify compromised hosts by identifying traffic 388 destined to IP addresses associated with the command and control 389 of botnets. In addition, bots can be idenfied when a remote host 390 is under distribute attack because computers participating in the 391 attack will likely be infected by a bot. 393 d. An ISP may use DNS-based techniques to perform detection. For 394 example, a given classified bot may be known to query a specific 395 list of domain names at specific times or on specific dates (in 396 the example of the so-called "Conficker" bot), often by matching 397 DNS queries to a well known list of domains associated with 398 malware. In many cases such lists are distributed by or shared 399 using third parties, such as threat data clearinghouses. 400 Alternative dynamic DNS based techniques may look for 401 associations of domain names with known bad actor lists and 402 networks with poor reputations, or heuristic techniques that rank 403 the domain name based upon previously identified botnet usage and 404 bot characteristics. 406 e. User complaints: Because bot infected hosts are frequently used 407 to send spam or participate in DDoS attacks, the ISP servicing 408 those hosts will normally receive complaints about the malicious 409 network traffic. Those complaints may be sent to RFC2142- 410 specified [RFC2142] role accounts, such as abuse@ or postmaster@ 411 or to abuse or security addresses specified by the site as part 412 of its WHOIS (or other) contact data. 414 f. ISPs may also discover likely bot infected hosts located at other 415 sites; when legally permissible or otherwise an industry accepted 416 practice in a particular market region, it may be worthwhile for 417 ISPs to share evidence relating to those compromised hosts with 418 the relevant remote ISP, with security researchers, and with 419 blocklist operators. 421 g. ISP's may operate or subscribe to services that provide 422 sinkholing or honeynet capabilities. This enable the ISP to 423 obtain realtime lists of bot infected computers as they attempt 424 to join the larger botnet or propagate. These technologies may 425 allow the ISP to enumerate bot infections within their customer 426 population. 428 5.2. Notification to Internet Users 430 Once an ISP has detected a bot, or the strong likelihood of a bot, 431 steps should be undertaken to inform the Internet user that they may 432 have a bot related problem. Depending upon a range of factors, from 433 the technical capabilities of the ISP, to the technical attributes of 434 their network, financial considerations, available server resources, 435 available organizational resources, the number of likely infected 436 computers detected at any given time, and the severity of any 437 possible threats, among many other things, an ISP will decide the 438 most appropriate method or methods for providing notification to one 439 or more of their customers or Internet users. Such notification 440 methods may include one or more of the following, as well as other 441 possible methods not described below. It is important to note that 442 none of these methods are guaranteed to be successful, as each has 443 its own set of limitations. In addition, in some cases, and ISP may 444 determine that a combination of two or more methods is most 445 appropriate. Finally, notification is also considered time 446 sensitive; if the user does not receive or view the notification or a 447 timely basis, then a particular bot could launch an attack, exploit 448 the user, or cause other harm. If possible, an ISP should establish 449 a preferred means of communication when the subscriber first signs up 450 for service. As a part of the notification process, ISPs should 451 maintain a record of the allocation of IP addresses to subscribers 452 for such a period as allows any bot detection technology to be 453 accurately able to link an infected IP address to a subscriber. This 454 record should only be maintained for a period which is consonant with 455 the protection of the privacy of the individual subscriber. 457 One important factor to bear in mind is that notification to end 458 users needs to be defended against spoofing by third parties. This 459 must be done to protect against the possibility of notifications 460 being spoofed and used by bots to deliver additional malware. 462 5.2.1. Email Notification 464 This is probably the most common form of notification used by ISPs. 465 One drawback of using email is that it is not guaranteed to be viewed 466 within a reasonable time frame, if at all. The user may be using a 467 different primary email address than that which they have provided to 468 the ISP. In addition, some ISPs do not provide an email account at 469 all, as part of a bundle of Internet services, and/or do not have a 470 need for or manner in which to request or retain the primary email 471 addresses of Internet users of their networks. Another possibility 472 is that the user, their email client, and/or their email servers 473 could determine or classify such a notification as spam, which could 474 delete the message or otherwise file it in an email folder that the 475 user may not check on a regular and/or timely basis. Bot masters 476 have also been known to impersonate the ISP or trusted sender and 477 send fradulant emails to the users. This technique of solical 478 engineering often leads to new bot infestations. Finally if the 479 user's email credentials are compromised, then a hacker and/or a bot 480 could simply login to the user's email account and delete the email 481 before it is read by the user. 483 5.2.2. Telephone Call Notification 485 A telephone call may be an effective means of communication in 486 particularly high-risk situations. However, telephone calls may not 487 be feasible due to the cost of making a large number of times, as 488 measured in either time, money, organizational resources, server 489 resources, or some other means. In addition, there is no guarantee 490 that the user will answer their phone. To the extent that the 491 telephone number called by the ISP can be answered by the infected 492 computing device, the bot on that computer may be able to disconnect, 493 divert, or otherwise interfere with an incoming call. Users may also 494 interpret such a telephone notification as a telemarketing call and 495 as such not welcome it, or not accept the call at all. Finally, even 496 if a representative of the ISP is able to connect with and speak with 497 a user, that user is very likely to lack the necessary technical 498 experience to understand or be able to effectively deal with the 499 threat. 501 5.2.3. Postal Mail Notification 503 This form of notification is probably the least popular means of 504 communication, due to both preparation time, delivery time and cost 505 however, it may be more effective than email even when delivering an 506 identical message. Optionally the notification of bot infection can 507 be printed on the bill when the subscriber is taking a billable 508 service. 510 5.2.4. Walled Garden Notification 512 Placing a user in a walled garden is another approach that ISPs may 513 take to notify users. A walled garden refers to an environment that 514 controls the information and services that a subscriber is allowed to 515 utilize and what network access permissions are granted. This is an 516 effective technique because it could be able to block all 517 communication between the bot and the command and control channel, 518 which may impair the ability of a bot to disrupt or block attempts to 519 notify the user. 521 While in many cases, the user is almost guaranteed to view the 522 notification message and take any appropriate remediation actions, 523 this approach poses can pose other challenges. For example, it is 524 not always the case that a user is actively using a computer that 525 uses a web browser or which has a web browser actively running on it. 526 In one case, a user could be playing a game online, via the use of a 527 dedicated, Internet-connected game console. In another case, the 528 user may not be using a computer with a web browser when they are 529 placed in the walled garden and may instead be in the course of a 530 telephone conversation, or may be expecting to receive a call, using 531 a Voice Over IP (VOIP) device of some type. As a result, the ISP may 532 feel the need to maintain a potentially lengthy white list of domains 533 which are not subject to the typical restrictions of a walled garden, 534 which could well prove to be an onerous task, from an operational 535 perspective. 537 The ISP has several options to determine when to let the user out of 538 the walled garden. One approach may be to let the user determine 539 when to exit. This option is suggested when the purpose of the 540 walled garden is to notify users and provide information on 541 remediation only, particularly since notification is not a guarantee 542 of successful remediation. It could also be the case that, for 543 whatever reason, the user makes the judgment that they cannot then 544 take the time to remediate their computer and that other online 545 activities which they would like to resume are more important. Exit 546 from the walled garden should involve require process to verify that 547 it is indeed the user who is requesting exit from the walled garden 548 and not the bot. 550 Once the user acknowledges the notification, then the user decides to 551 either remediate and then exit the walled garden, or exit the walled 552 garden without addressing the issue. Another approach may be to 553 enforce a stricter policy and require the user to clean the computer 554 prior to permitting the user to exit the walled garden, though this 555 may not be technically feasible depending upon the type of bot, 556 obfuscation techniques employed by a bot, and/or a range of other 557 factors. Thus, the ISP may also need to support tools to scan the 558 infected computer and determine whether it is still infected or rely 559 on user judgment that the bot has been disabled or removed. One 560 challenge with this approach is that if the user has multiple 561 computers sharing a single IP address, such as via a common home 562 gateway device which performs Network Address Translation (NAT), then 563 the ISP may need to determine from user feedback or other means that 564 all affected computers have been remediated, which may or may not be 565 technically feasible. 567 A list of well known addresses for both operating system vendors and 568 security vendors should be created. This can be referenced when 569 allowing access from the walled garden by end users in search of 570 operating system and application patches. 572 5.2.5. Instant Message Notification 574 Instant Message (IM): Instant messaging provides the ISP with a 575 simple means to communicate with the user. There are several 576 advantages to using IM which makes it an attractive option. If the 577 ISP provides IM service and the user subscribes to it then the user 578 can be notified easily. IM based notification can be cost effective 579 means to communicate with the use. This can be achieved by signing 580 up for IM service with the various popular IM providers and 581 programatically messaging, if permitted by the acceptable usage 582 policy, the notifications. However, IM based notification can also 583 be done manually by the ISP's support staff. Ideally, the ISP should 584 allow the user to register the IM identity and seek permission to be 585 contacted via this means. If the IM service provider supports 586 offline messaging the user can be notified regardless of their signed 587 in status. Essentially a message can be sent and when the user signs 588 in they would receive it. There are several drawbacks with this 589 communications method. There is a high probability that subscriber 590 may interpret the communication to be spam and as such ignore it. 591 Not every user uses IM and/or the user may not provide their IM 592 identity to the ISP so some alternative means have to be used. There 593 maybe a privacy concern when the communication between the ISP and 594 the end user is not secure and over a third party network and/or IM 595 service. As such the notification must be discreet and not provide 596 any personally identifiable information. 598 5.2.6. Short Message Service (SMS) Notification 600 Short Message Service (SMS): SMS allows the ISP send a brief 601 description of the problem to notify the user of the issue. The ISP 602 should allow users to register their mobile number for notifications 603 and also allow users to opt out if they do not wish to be notified. 604 The primary advantage of SMS is that users are used to receiving text 605 messages and are likely to read them. Users may not act on the 606 notification immediately if they are not in front of their computer 607 system. One disadvantage is that ISPs may have to follow up with an 608 alternate means of notification if not all of the necessary 609 information maybe conveyed in one message. This is becuase SMS 610 messages are limited to 140 characters. Another disadvantage with 611 SMS is the cost associated with it. The ISP has to either build its 612 own SMS gateway to interface with the various wireless service 613 providers or use a third party provider to notify users. It is 614 recommended that the ISP absorb the cost of notification and should 615 always state in the notification that the message is free of charge 616 to the user. Another small disadvantage is that it is possible to 617 notify the wrong user if the intended user changes their mobile 618 number but forgets to update it with the ISP. 620 5.2.7. Web Browser Notification 622 Near real-time notification to the user's web browser is another 623 technique that may be utilized for notifying the user, though how 624 such a system might operate is outside the scope of this document. 625 Such a notification could have a comparative advantage over a walled 626 garden notification, in that it does not restrict traffic to a 627 specified list of destinations in the same way that a walled garden 628 by definition would. However, as with a walled garden notification, 629 there is no guarantee that a user is at any given time making use of 630 a web browser, though such a system could certainly provide a 631 notification when such a browser is eventually used. Compared to a 632 walled garden, a web browser notification is probably preferred from 633 the perspective of Internet users, as it does not have the risk of 634 disrupting non-web sessions, such as online games, etc. (as noted in 635 Section 5.2.4). 637 5.3. Remediation of Bot Infected Machines 639 This section covers the different options available to remediate a 640 computer, which means to remove, disable, or otherwise render a bot 641 harmless. Prior to this step, an ISP has detected the bot, notified 642 the user that one of their computers is infected with a bot, and now 643 has to provide some means to clean the PC. The generally recommended 644 approach is to provide the necessary tools and education to the user 645 so that they may perform bot remediation themselves. 647 For example, this may include the creation of a special Security Web 648 Portal. This should be a well-publicized security portal to which a 649 user with a bot problem can be directed to for remediation. This 650 Security Web Portal should clearly explain why the user was notified 651 and may include an explanation of what bots are and the threats that 652 they pose. There should be a clear explanation of the steps that the 653 user should take in order to clean the computers and provide 654 information on how users can keep the computer free of future 655 infections. The Security Web Portal should have a guided process 656 that takes non technical users through the remediation process. 658 In terms of the text user to explain what bots are and the threat 659 they pose, something simple such as this may suffice: 661 "What is a bot? A bot is a piece of software, generally installed on 662 your machine without your knowledge, which either sends spam or tries 663 to steal your personal information. They can be very difficult to 664 spot, though you may have noticed that your computer is running much 665 more slowly than usual or you notice regular disk activity even when 666 you are not doing anything. Ignoring this problem is not really an 667 option since your personal information is currently at risk. Thus, 668 bots need to be removed to protect your data and your personal 669 information." 671 It is also important to note that it may not be immediately apparent 672 to the Internet user precisely which device has been or which 673 multiple devices have been infected with a particular bot. This is 674 because of the user's home-networking configurations and the growing 675 prevalence of IP enabled devices within a household that now connect 676 to the public Internet and/or Private IP networks. The consequence 677 of this for an ISP is that remediation advice may not ultimately be 678 actionable by the Internet user. For example, the Internet user may 679 be operating a computer, a notebook, a video console and multimedia 680 system on their personal network. All of these device may connect to 681 the Internet via a single gateway appliance. Any of these devices 682 can be infected with a bot through a number of vectors. yet the 683 remediation advice is likely to be quite different and may or may not 684 be directly serviceable by the Internet user. Diligence needs to be 685 taken by the ISP in understanding the specific nature of the device 686 that has been infected with a bot, and providing appropriate 687 remediation advice. 689 5.4. Guided Remediation Process 691 Minimally the Guided Remediation Process should include options 692 and/or recommendations on how a user should: 694 1. Backup personal Documents, for example: "Before you start, make 695 sure to back up all of your important data. (You should do this 696 on a regular basis anyway.) You can back up your files manually 697 or using a system back-up software utility, which may be part of 698 your Operating System (OS). You can back your files up to a USB 699 Thumb Drive (aka USB Key), a CD/DVD-ROM, an external hard drive, 700 or a network file server." 702 2. Download OS patches and Anti-Virus (A/V) software updates. For 703 example, links could be provided to Microsoft Windows updates at 704 http://update.microsoft.com/microsoftupdate/v6/ 705 default.aspx?ln=en-us as well as to Apple MacOS updates at 706 http://support.apple.com/kb/HT1338?viewlocale=en_US. 708 3. Explain how to configure the computer to automatically install 709 updates for the OS, A/V and other common Web Browsers such as 710 Microsoft Internet Explorer, Mozilla Firefox, Apple Safari, 711 Opera, and Google Chrome. 713 4. The flow should also have the option for users to get 714 professional assistance if they are unable to remove the bots 715 themselves. If purchasing third party assistance, then the user 716 should be encouraged to pre-determine how much they are willing 717 to pay for that help. If the computer that is being remediated 718 is old and can easily be replaced with a new, faster, larger and 719 more reliable system for three or four hundred dollars, the it 720 makes no sense to spend five or six hundred dollars to fix the 721 old computer, for example. On the other hand, if the customer 722 has a brand new computer that cost several thousand dollars, it 723 might make perfect sense to spend the money in attempting to 724 remediate it. 726 5. To continue, regardless of whether the user or a knowledgeable 727 technical assistant is working on remediating the computer, their 728 first task should be to determine which of multiple potentially- 729 infected machines may be the one that needs attention (in the 730 common case of multiple computers in a home network). Sometimes, 731 as in cases where there is only a single directly-attached 732 computer, or the user has been noticing problems with one of 733 their computers, this can be easy. Other times, it may be more 734 difficult. If the user is behind a home gateway/router, then the 735 first task may be to ascertain which of the machines is infected. 736 In some cases the user may have to check all machines to identify 737 the infected one. 739 6. User surveys to solicit feedback on whether the notification and 740 remediation process is effective and what recommended changes 741 could be made in order to improve the ease, understandability, 742 and effectiveness the remediation process. 744 7. If the user is interested in reporting his or her computer's bot 745 infection to an applicable law enforcement authority, then the 746 computer effectively becomes a cyber "crime scene" and should not 747 be mitigated unless or until law enforcement has collected the 748 necessary evidence. For individuals in this situation, the ISP 749 should refer them to local, state, federal, or other relevant 750 computer crime offices. (Note: Some "minor" incidents, even if 751 highly traumatic to the user, may not be sufficiently serious for 752 law enforcement to commit some of their limited resources to an 753 investigation.) 755 6. Security Considerations 757 There are no security considerations to include at this time. 759 7. IANA Considerations 761 There are no IANA considerations in this document. 763 8. Acknowledgements 765 The authors wish to acknowledge the following individuals and 766 organisations for their review and feedback of this document: 768 Jonathan Curtis 770 Jeff Chan 772 Roland Dobbins 774 Eliot Gillum 776 Messaging Anti-Abuse Working Group (MAAWG) 778 Jose Nazario 780 Gunter Ollmann 782 Eric Ziegast 784 9. Informative references 786 [RFC1459] Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol", 787 RFC 1459, May 1993. 789 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 790 Requirement Levels", BCP 14, RFC 2119, March 1997. 792 [RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND 793 FUNCTIONS", RFC 2142, May 1997. 795 [RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version 796 9", RFC 3954, October 2004. 798 Appendix A. Document Change Log 800 [RFC Editor: This section is to be removed before publication] 802 -01 version: 804 o -01 version published 806 Appendix B. Open Issues 808 [RFC Editor: This section is to be removed before publication] 810 Could use some informational references in Section 3 812 Fix the odd list spacing in Section 5.1 814 Consider revision of the OS update links, to simplify them. 816 Add some point about notification to large networks may not be useful 817 -- such as coffee shops or hotels with WiFi networks. 819 Authors' Addresses 821 Jason Livingood 822 Comcast Cable Communications 823 One Comcast Center 824 1701 John F. Kennedy Boulevard 825 Philadelphia, PA 19103 826 US 828 Email: jason_livingood@cable.comcast.com 829 URI: http://www.comcast.com 831 Nirmal Mody 832 Comcast Cable Communications 833 One Comcast Center 834 1701 John F. Kennedy Boulevard 835 Philadelphia, PA 19103 836 US 838 Email: nirmal_mody@cable.comcast.com 839 URI: http://www.comcast.com 840 Mike O'Reirdan 841 Comcast Cable Communications 842 One Comcast Center 843 1701 John F. Kennedy Boulevard 844 Philadelphia, PA 19103 845 US 847 Email: michael_oreirdan@cable.comcast.com 848 URI: http://www.comcast.com