Internet Engineering Task Force                             J. Livingood
Internet-Draft                                                   N. Mody
Intended status: Informational                              M. O'Reirdan
Expires: February 27, 2010                                       Comcast
                                                         August 26, 2009

   Recommendations for the Remediation of Bots in Large ISP Networks

Status of this Memo

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   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.


   This document contains recommendations on how large Internet Service
   Providers (ISPs) can manage the effects of large numbers of bot
   infected computers used by their subscribers via various remediation
   techniques.  At the time that this document was published, computers
   infected by bots and the users of those computers comprise a
   substantial number of users for large ISPs.  Those Internet users are
   exposed to risks such as loss of personal data, increased
   susceptibility to online fraud and/or phishing, and becoming an
   inadvertent participant in or component of an online crime, spam,
   and/or phishing network.  Mitigating the effects of and remediating
   the installations of bots affecting large numbers of Internet users
   will make it more difficult for botnets to operate and could reduce
   the level of online crime on the Internet in general and/or on a
   particular ISP's network.

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Table of Contents

   1.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  4
   2.  Key Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Introduction and Problem Statement . . . . . . . . . . . . . .  5
   4.  Important Notice of Limitations  . . . . . . . . . . . . . . .  7
   5.  Detection, Notification and Remediation  . . . . . . . . . . .  7
     5.1.  Detection of Bots  . . . . . . . . . . . . . . . . . . . .  7
     5.2.  Notification to Internet Users . . . . . . . . . . . . . . 11
     5.3.  Remediation of Bot Infected Machines . . . . . . . . . . . 15
     5.4.  Guided Remediation Process . . . . . . . . . . . . . . . . 16
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
   9.  Informative references . . . . . . . . . . . . . . . . . . . . 18
   Appendix A.  Document Change Log . . . . . . . . . . . . . . . . . 18
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19

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1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

2.  Key Terminology

   This section defines the key terms used in this document.

2.1.  Bots

   A "bot" (derived from the word "robot") refers to a program that is
   surreptitiously installed on a system in order to enable that system
   to automatically (or semi-automatically) perform a task or set of
   tasks typically under the command and control of a remote
   administrator, or "bot master."  Bots are also known as "zombies."
   It is important to note that there are 'good' bots.  Such benign bots
   are often found in such environments such as gaming and Internet
   Relay Chat (IRC) [RFC1459], where a continual, interactive presence
   can be a requirement for participating in the games, interacting with
   a computing resource, or other purposes.  However, for the purposes
   of this document, all mention of bots should assume that the bots
   involved are malicious in nature.  Such malicious bots shall
   generally be assumed to have been deployed without the permission or
   conscious understanding of a particular Internet user.  Thus, without
   a user's knowledge, bots may transform the user's computing device
   into a platform from which malicious activities are conducted.

2.2.  Bot Networks, or Botnets

   These are defined as concerted networks of bots capable of acting on
   instructions generated remotely.  The malicious activities are either
   focused on the information on the local machine or acting to provide
   services for remote machines.  Bots are highly customizable so they
   can be programmed to do many things.  The major malicious activities
   include: identity theft, spam, denial of service attacks, key-
   logging, fraudulent DNS (pharming), proxy services, fast flux hosting
   and click fraud.  Infection vectors include un-patched operating
   systems, software vulnerabilities, weak/non-existent passwords,
   malicious websites, un-patched browsers, malware, vulnerable helper
   applications and social engineering techniques to gain access to the
   user's computer.  The detection and destruction of bots is an ongoing
   issue and also a constant battle between the internet security
   community, network security engineers and bot developers.  Initially
   bots used IRC to communicate but were easy to shutdown if the command
   and control server was identified and deactivated.  However, newer

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   command and control topologies employed by bot masters make them much
   more resistant to deactivation.  With the introduction of P2P, HTTP
   and other resilient communication protocols along with the widespread
   adoption of encryption, bots are considerably more difficult to
   identify and isolate from typical network usage.  As a result
   increased reliance is being placed on anonmaly detection and
   behavioral analysis, both locally and remotely, to identify bots.

2.3.  Computer

   A computer, as used in the context of this document, is intended to
   encompass the computing devices networked and reliant upon the
   Internet for communications, software updates and functional
   operation.  This encompasses devices used directly by Internet users
   such as personal computers, including laptops, desktops, and
   netbooks, as well as mobile phones, smart phones, home gateway
   devices, and other end user computing devices which are connected or
   can connect to the public Internet and/or private IP networks.

   Increasingly, other household systems and devices contain embedded
   computers which are connected or can connect to the public Internet
   and/or private IP networks.  However, these devices may not be under
   interactive control of the Internet user.  Smart home technologies
   that manage energy consumption and monitor household appliances or
   environments have become more common and are more often networked.
   This is with or without the homeowners knowledge or ability to alter

2.4.  Malware

   This is short for "malicious software."  In this case, malicious bots
   are considered a subset of malware, which could also include viruses
   and other similar types of software.  Internet users can sometimes
   cause their computer to be infected with malware, which may include a
   bot or cause a bot to install itself, via inadvertently accessing a
   specific website, downloading a specific file, or other activities.

   Alternatively, Internet accessible devices may become infected with
   malware through externally initiated malicious activities such as the
   exploitation of vulnerabilities or the brute forced guessing of
   access credentials.

3.  Introduction and Problem Statement

   Computers used by Internet users, which in this case are customers of
   an Internet Service Provider (ISP), can be infected with malware
   which may contain and/or install one or more bots on a computer.

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   This can present a major problem for an ISP for a number of reasons
   (not to mention of course the problems created for users).  First,
   these bots can be used to send spam, in some cases very large volumes
   of spam.  This spam can result in extra cost for the ISPs in terms of
   wasted network, server, and/or personnel resources, among many other
   potential costs or side effects.  Such spam can also negatively
   affect the reputation of the ISP, their customers, and the email
   reputation of the IP address space used by the ISP (often referred to
   simply as "IP reputation").

   In addition, these bots can act as platforms for directing,
   participating in, or otherwise conducting attacks on critical
   Internet infrastructure.  Bots are frequently used as part of
   concerted Distributed Denial of Service (DDoS) attacks for criminal,
   political or other motivations.  For example, bots have been used to
   attack Internet resources and infrastructure ranging from web sites,
   to email servers and DNS servers, as well as the critical Internet
   infrastructure of entire countries.  Motivations for such coordinated
   DDoS attacks can range from criminal extortion attempts through to
   online protesting and nationalistic fervor.

   While any computing device can be infected with bots, the majority of
   bot infections affect the personal computers used by Internet end
   users.  As a result of the role of ISPs in providing IP connectivity,
   among many other services, to Internet users, these ISPs are in a
   unique position to be able to attempt to detect and observe bot nets
   operating in their networks.  Furthermore, ISPs may also be in a
   unique position to be able to communicate to Internet users which are
   their customers, when customers computers may have been determined to
   have been or possibly have been infected with one or more bots.

   From an end user perspective, knowing that their computer has been
   infected with one or more bots is very important information.  Once
   they know this, they can take steps to remove the bot, protect
   themselves in the future, and resolve any problems which may stem
   from the bot infection.  Given that bots can drain the local
   computing and network resources, enable theft of personal information
   (including personal financial information), enable the computer to be
   used from criminal activities (that may result in the Internet user
   being legally culpable), destroy or leave the PC in an unrecoverable
   state via 'kill switch' bot technologies, it is important to notify
   the user that they may be infected with a bot.

   As a result, the intent of this document is to provide a guide to
   ISPs and other organizations for the remediation of these computers
   infected with bots, so as to reduce the size of bot nets and minimize
   the potential harm that bots can inflict upon Internet infrastructure
   generally, as well as on individual Internet users.  Efforts by ISPs

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   and other organizations could therefore, over time, reduce the pool
   of computers infected with bots on the Internet, which in turn could
   result in smaller bot nets with less capability for disruption.

4.  Important Notice of Limitations

   The techniques described in this document in no way guarantee the
   remediation of all bots.  Bot removal is potentially a task requiring
   specialized knowledge, skills and tools, and may be beyond the
   ability of average users.  Attempts at bot removal may frequently be
   unsuccessful, or only partially successful, and may leave a user's
   system in an unstable and unsatisfactory state or even still
   infected.  Attempts at bot removal can also result in side effects
   ranging from a loss of data or other files, all the way through
   partial or complete loss of system usability.

   In general, the only way a user can be sure they have removed some of
   today's increasingly sophisticated malware is by "nuking-and-paving"
   the system: reformatting the drive, reinstalling the operating system
   and applications (including all patches) from scratch, and then
   restoring user files from a clean backup.  However the introduction
   of BIOS based malware may mean that in some cases, this will not be
   enough and may prove to be more than any end user can be reasonably
   expected to resolve.

   Devices with embedded operating systems, such as video gaming
   consoles and smart home appliances, will most likely be beyond a
   user's capability to remediate by themselves, and will typically
   require the aid of vendor specific advice, updates and tools.  Care
   must be taken when imparting remediation advice to Internet users
   given the increasingly wide array of computing devices that can be,
   or could be, bot infected in the future.

5.  Detection, Notification and Remediation

   The potential mitigation of bots is accomplished through a process of
   detection, notification to Internet users, and remediation of that
   bot with a variety of tools.

5.1.  Detection of Bots

   An ISP must first identify that an Internet user, in this case a user
   that is assumed to be their customer or otherwise connected to the
   ISP's network, is determined to be infected, or likely to have been
   infected with a bot.  The ISP should attempt to detect the presence
   of bots using methods, processes, and tools which maintain the

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   privacy of the personally identifiable information of their
   customers.  The ISP also should not block legitimate traffic in the
   course of bot detection, and should instead employ detection methods,
   tools, and processes which seek to be non-disruptive, as well as
   being transparent to Internet users.

   Detection methods, tools, and processes may include things such as
   analysis of specific network and/or application traffic flows (such
   as traffic to an email server), analysis of aggregate network and/or
   application traffic data, data feeds received from other ISPs and
   organizations (such as lists of the ISP's IP addresses which have
   been reported to have sent spam), feedback from the ISP's customers
   or other Internet users, as well as a wide variety of other
   possibilities.  It is likely that a combination of multiple bot
   detection data points will prove to be an effective approach in order
   to corroborate information of varying dependability or consistency,
   as well as to avoid or minimize the possibility of false positive
   identification of computers.  Detection should also, where possible
   and feasible, attempt to classify a bot in order to confirm that it
   is malicious in nature, estimate the variety and severity of threats
   it may pose (such as spam bot, key-logging bot, file distribution
   bot, etc.), and to determine potential methods for eventual
   remediation.  However, given the dynamic nature of botnet management
   and the criminal incentives to seek quick financial rewards, botnets
   frequently update or change their core malicious capabilities.  As a
   consequence, botnets that are initially detected and classified by
   the ISP need to be continuously monitored and tracked in order to
   correctly identify the threat they pose at any particular point in

   Detection is also time-sensitive.  If complex analysis is required
   and multiple confirmations are needed to confirm a bot is indeed
   present, then it is possible that the bot will do its damage (to
   either the infected computer or a remotely targeted system) before it
   can be stopped.  This may mean that an ISP may need to balance the
   desire or need to definitively classify and/or confirm a bot, which
   may take an extended period of time, with the ability to predict the
   strong likelihood of a bot in a very short period of time.  This also
   means that Internet users may benefit from the deployment of client-
   based software protections or other software tools, which can enable
   rapid performance of heuristically-based detection bot activity, such
   as the detection of a bot as it starts to communicate a bot net and
   execute some type of command.  Any bot detection systems should also
   be capable of learning and adapting, either via manual intervention
   or automatically, in order to cope with a rapidly evolving threat.

   As noted above, detection methods, tools, and processes should ensure
   that privacy of customers' personally identifiable information is

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   maintained.  While bot detection methods, tools, and processes are
   similar to spam and virus defenses deployed by the ISP for the
   benefits of their customers (and may be directly related to those
   defenses), attempts to detect bots should take into account the need
   of an ISP to take care to ensure that such personally identifiable
   information is properly protected.  Finally, depending upon the
   geographic region within which an ISP operates, certain methods
   relating to bot detection may need to be included in relevant terms
   of service documents or other documents which are available to the
   customers of a particular ISP.

   There are several bot detection methods, tools, and processes that an
   ISP may choose to utilize, as noted in the list below.  It is
   important to note that the technical solutions available are
   relatively immature, and are likely to change over time, and to
   evolve rapidly in the coming years.  While these items are described
   in relation to ISPs, they may also be applicable to organizations
   operating other networks, such as campus networks and enterprise

   a.  Where legally permissible or otherwise an industry accepted
       practice in a particular market region, an ISP may in some manner
       "scan" their IP space in order to detect un-patched or otherwise
       vulnerable hosts.  This may provide the ISP with the opportunity
       to easily identify Internet users who appear to already be or are
       at great risk of being infected with a bot.  ISP's should note
       that some types of port scanning may leave network services in a
       hung state or render them unusable due to common frailties, and
       that many modern firewall and host-based intrusion detection
       implementations may alert the Internet user to the scan.  As a
       result the scan may be interpreted as a malicious attack against
       the computer.  Vulnerability scanning has a higher probability of
       leaving accessible network services and applications in a damaged
       state and will often result in a higher probability of detection
       by the Internet user and subsequent interpretation as a targeted
       attack.  Depending upon the vulnerability being scanned, some
       automated methods of vulnerability checking may result in data
       being altered or created afresh on the Internet users computer
       which be a problem in many legal environments.

   b.  An ISP may also communicate and share selected data, via feedback
       loops or other mechanisms, with various third parties.  Feedback
       loops are consistently formatted feeds of real-time (or nearly
       real-time) abuse reports offered by threat data clearinghouses,
       security alert organizations, other ISPs, and other
       organizations.  The data may include, but is not limited to,
       lists of the IP addresses computers which have or are likely to
       have a bot running, domain names or fully qualified domain names

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       (FQDNs) known to host malware and/or be involved in the command
       and control of botnets, IP addresses know to host malware and/or
       be involved in the command and control of botnets, recently
       tested or discovered techniques or detecting or remediating bot
       infections, new threat vectors, and other relevant information.
       Good examples of this include SNDS from Microsoft, XBL and PBL
       from Spamhaus and DSHIELD AS tool from SANS

   c.  An ISP may use Netflow [RFC3954] or other similar passive network
       monitoring to identify network anomalies that may be indicative
       of botnet attacks or bot communications.  For example, an ISP may
       be able to identify compromised hosts by identifying traffic
       destined to IP addresses associated with the command and control
       of botnets.  In addition, bots can be idenfied when a remote host
       is under distribute attack because computers participating in the
       attack will likely be infected by a bot.

   d.  An ISP may use DNS-based techniques to perform detection.  For
       example, a given classified bot may be known to query a specific
       list of domain names at specific times or on specific dates (in
       the example of the so-called "Conficker" bot), often by matching
       DNS queries to a well known list of domains associated with
       malware.  In many cases such lists are distributed by or shared
       using third parties, such as threat data clearinghouses.
       Alternative dynamic DNS based techniques may look for
       associations of domain names with known bad actor lists and
       networks with poor reputations, or heuristic techniques that rank
       the domain name based upon previously identified botnet usage and
       bot characteristics.

   e.  User complaints: Because bot infected hosts are frequently used
       to send spam or participate in DDoS attacks, the ISP servicing
       those hosts will normally receive complaints about the malicious
       network traffic.  Those complaints may be sent to RFC2142-
       specified [RFC2142] role accounts, such as abuse@ or postmaster@
       or to abuse or security addresses specified by the site as part
       of its WHOIS (or other) contact data.

   f.  ISPs may also discover likely bot infected hosts located at other
       sites; when legally permissible or otherwise an industry accepted
       practice in a particular market region, it may be worthwhile for
       ISPs to share evidence relating to those compromised hosts with
       the relevant remote ISP, with security researchers, and with
       blocklist operators.

   g.  ISP's may operate or subscribe to services that provide
       sinkholing or honeynet capabilities.  This enable the ISP to
       obtain realtime lists of bot infected computers as they attempt

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       to join the larger botnet or propagate.  These technologies may
       allow the ISP to enumerate bot infections within their customer

5.2.  Notification to Internet Users

   Once an ISP has detected a bot, or the strong likelihood of a bot,
   steps should be undertaken to inform the Internet user that they may
   have a bot related problem.  Depending upon a range of factors, from
   the technical capabilities of the ISP, to the technical attributes of
   their network, financial considerations, available server resources,
   available organizational resources, the number of likely infected
   computers detected at any given time, and the severity of any
   possible threats, among many other things, an ISP will decide the
   most appropriate method or methods for providing notification to one
   or more of their customers or Internet users.  Such notification
   methods may include one or more of the following, as well as other
   possible methods not described below.  It is important to note that
   none of these methods are guaranteed to be successful, as each has
   its own set of limitations.  In addition, in some cases, and ISP may
   determine that a combination of two or more methods is most
   appropriate.  Finally, notification is also considered time
   sensitive; if the user does not receive or view the notification or a
   timely basis, then a particular bot could launch an attack, exploit
   the user, or cause other harm.  If possible, an ISP should establish
   a preferred means of communication when the subscriber first signs up
   for service.  As a part of the notification process, ISPs should
   maintain a record of the allocation of IP addresses to subscribers
   for such a period as allows any bot detection technology to be
   accurately able to link an infected IP address to a subscriber.  This
   record should only be maintained for a period which is consonant with
   the protection of the privacy of the individual subscriber.

   One important factor to bear in mind is that notification to end
   users needs to be defended against spoofing by third parties.  This
   must be done to protect against the possibility of notifications
   being spoofed and used by bots to deliver additional malware.

5.2.1.  Email Notification

   This is probably the most common form of notification used by ISPs.
   One drawback of using email is that it is not guaranteed to be viewed
   within a reasonable time frame, if at all.  The user may be using a
   different primary email address than that which they have provided to
   the ISP.  In addition, some ISPs do not provide an email account at
   all, as part of a bundle of Internet services, and/or do not have a
   need for or manner in which to request or retain the primary email
   addresses of Internet users of their networks.  Another possibility

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   is that the user, their email client, and/or their email servers
   could determine or classify such a notification as spam, which could
   delete the message or otherwise file it in an email folder that the
   user may not check on a regular and/or timely basis.  Bot masters
   have also been known to impersonate the ISP or trusted sender and
   send fradulant emails to the users.  This technique of solical
   engineering often leads to new bot infestations.  Finally if the
   user's email credentials are compromised, then a hacker and/or a bot
   could simply login to the user's email account and delete the email
   before it is read by the user.

5.2.2.  Telephone Call Notification

   A telephone call may be an effective means of communication in
   particularly high-risk situations.  However, telephone calls may not
   be feasible due to the cost of making a large number of times, as
   measured in either time, money, organizational resources, server
   resources, or some other means.  In addition, there is no guarantee
   that the user will answer their phone.  To the extent that the
   telephone number called by the ISP can be answered by the infected
   computing device, the bot on that computer may be able to disconnect,
   divert, or otherwise interfere with an incoming call.  Users may also
   interpret such a telephone notification as a telemarketing call and
   as such not welcome it, or not accept the call at all.  Finally, even
   if a representative of the ISP is able to connect with and speak with
   a user, that user is very likely to lack the necessary technical
   experience to understand or be able to effectively deal with the

5.2.3.  Postal Mail Notification

   This form of notification is probably the least popular means of
   communication, due to both preparation time, delivery time and cost
   however, it may be more effective than email even when delivering an
   identical message.  Optionally the notification of bot infection can
   be printed on the bill when the subscriber is taking a billable

5.2.4.  Walled Garden Notification

   Placing a user in a walled garden is another approach that ISPs may
   take to notify users.  A walled garden refers to an environment that
   controls the information and services that a subscriber is allowed to
   utilize and what network access permissions are granted.  This is an
   effective technique because it could be able to block all
   communication between the bot and the command and control channel,
   which may impair the ability of a bot to disrupt or block attempts to
   notify the user.

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   While in many cases, the user is almost guaranteed to view the
   notification message and take any appropriate remediation actions,
   this approach poses can pose other challenges.  For example, it is
   not always the case that a user is actively using a computer that
   uses a web browser or which has a web browser actively running on it.
   In one case, a user could be playing a game online, via the use of a
   dedicated, Internet-connected game console.  In another case, the
   user may not be using a computer with a web browser when they are
   placed in the walled garden and may instead be in the course of a
   telephone conversation, or may be expecting to receive a call, using
   a Voice Over IP (VOIP) device of some type.  As a result, the ISP may
   feel the need to maintain a potentially lengthy white list of domains
   which are not subject to the typical restrictions of a walled garden,
   which could well prove to be an onerous task, from an operational

   The ISP has several options to determine when to let the user out of
   the walled garden.  One approach may be to let the user determine
   when to exit.  This option is suggested when the purpose of the
   walled garden is to notify users and provide information on
   remediation only, particularly since notification is not a guarantee
   of successful remediation.  It could also be the case that, for
   whatever reason, the user makes the judgment that they cannot then
   take the time to remediate their computer and that other online
   activities which they would like to resume are more important.  Exit
   from the walled garden should involve require process to verify that
   it is indeed the user who is requesting exit from the walled garden
   and not the bot.

   Once the user acknowledges the notification, then the user decides to
   either remediate and then exit the walled garden, or exit the walled
   garden without addressing the issue.  Another approach may be to
   enforce a stricter policy and require the user to clean the computer
   prior to permitting the user to exit the walled garden, though this
   may not be technically feasible depending upon the type of bot,
   obfuscation techniques employed by a bot, and/or a range of other
   factors.  Thus, the ISP may also need to support tools to scan the
   infected computer and determine whether it is still infected or rely
   on user judgment that the bot has been disabled or removed.  One
   challenge with this approach is that if the user has multiple
   computers sharing a single IP address, such as via a common home
   gateway device which performs Network Address Translation (NAT), then
   the ISP may need to determine from user feedback or other means that
   all affected computers have been remediated, which may or may not be
   technically feasible.

   A list of well known addresses for both operating system vendors and
   security vendors should be created.  This can be referenced when

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   allowing access from the walled garden by end users in search of
   operating system and application patches.

5.2.5.  Instant Message Notification

   Instant Message (IM): Instant messaging provides the ISP with a
   simple means to communicate with the user.  There are several
   advantages to using IM which makes it an attractive option.  If the
   ISP provides IM service and the user subscribes to it then the user
   can be notified easily.  IM based notification can be cost effective
   means to communicate with the use.  This can be achieved by signing
   up for IM service with the various popular IM providers and
   programatically messaging, if permitted by the acceptable usage
   policy, the notifications.  However, IM based notification can also
   be done manually by the ISP's support staff.  Ideally, the ISP should
   allow the user to register the IM identity and seek permission to be
   contacted via this means.  If the IM service provider supports
   offline messaging the user can be notified regardless of their signed
   in status.  Essentially a message can be sent and when the user signs
   in they would receive it.  There are several drawbacks with this
   communications method.  There is a high probability that subscriber
   may interpret the communication to be spam and as such ignore it.
   Not every user uses IM and/or the user may not provide their IM
   identity to the ISP so some alternative means have to be used.  There
   maybe a privacy concern when the communication between the ISP and
   the end user is not secure and over a third party network and/or IM
   service.  As such the notification must be discreet and not provide
   any personally identifiable information.

5.2.6.  Short Message Service (SMS) Notification

   Short Message Service (SMS): SMS allows the ISP send a brief
   description of the problem to notify the user of the issue.  The ISP
   should allow users to register their mobile number for notifications
   and also allow users to opt out if they do not wish to be notified.
   The primary advantage of SMS is that users are used to receiving text
   messages and are likely to read them.  Users may not act on the
   notification immediately if they are not in front of their computer
   system.  One disadvantage is that ISPs may have to follow up with an
   alternate means of notification if not all of the necessary
   information maybe conveyed in one message.  This is becuase SMS
   messages are limited to 140 characters.  Another disadvantage with
   SMS is the cost associated with it.  The ISP has to either build its
   own SMS gateway to interface with the various wireless service
   providers or use a third party provider to notify users.  It is
   recommended that the ISP absorb the cost of notification and should
   always state in the notification that the message is free of charge
   to the user.  Another small disadvantage is that it is possible to

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   notify the wrong user if the intended user changes their mobile
   number but forgets to update it with the ISP.

5.2.7.  Web Browser Notification

   Near real-time notification to the user's web browser is another
   technique that may be utilized for notifying the user, though how
   such a system might operate is outside the scope of this document.
   Such a notification could have a comparative advantage over a walled
   garden notification, in that it does not restrict traffic to a
   specified list of destinations in the same way that a walled garden
   by definition would.  However, as with a walled garden notification,
   there is no guarantee that a user is at any given time making use of
   a web browser, though such a system could certainly provide a
   notification when such a browser is eventually used.  Compared to a
   walled garden, a web browser notification is probably preferred from
   the perspective of Internet users, as it does not have the risk of
   disrupting non-web sessions, such as online games, etc. (as noted in
   Section 5.2.4).

5.3.  Remediation of Bot Infected Machines

   This section covers the different options available to remediate a
   computer, which means to remove, disable, or otherwise render a bot
   harmless.  Prior to this step, an ISP has detected the bot, notified
   the user that one of their computers is infected with a bot, and now
   has to provide some means to clean the PC.  The generally recommended
   approach is to provide the necessary tools and education to the user
   so that they may perform bot remediation themselves.

   For example, this may include the creation of a special Security Web
   Portal.  This should be a well-publicized security portal to which a
   user with a bot problem can be directed to for remediation.  This
   Security Web Portal should clearly explain why the user was notified
   and may include an explanation of what bots are and the threats that
   they pose.  There should be a clear explanation of the steps that the
   user should take in order to clean the computers and provide
   information on how users can keep the computer free of future
   infections.  The Security Web Portal should have a guided process
   that takes non technical users through the remediation process.

   In terms of the text user to explain what bots are and the threat
   they pose, something simple such as this may suffice:

   "What is a bot?  A bot is a piece of software, generally installed on
   your machine without your knowledge, which either sends spam or tries
   to steal your personal information.  They can be very difficult to
   spot, though you may have noticed that your computer is running much

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   more slowly than usual or you notice regular disk activity even when
   you are not doing anything.  Ignoring this problem is not really an
   option since your personal information is currently at risk.  Thus,
   bots need to be removed to protect your data and your personal

   It is also important to note that it may not be immediately apparent
   to the Internet user precisely which device has been or which
   multiple devices have been infected with a particular bot.  This is
   because of the user's home-networking configurations and the growing
   prevalence of IP enabled devices within a household that now connect
   to the public Internet and/or Private IP networks.  The consequence
   of this for an ISP is that remediation advice may not ultimately be
   actionable by the Internet user.  For example, the Internet user may
   be operating a computer, a notebook, a video console and multimedia
   system on their personal network.  All of these device may connect to
   the Internet via a single gateway appliance.  Any of these devices
   can be infected with a bot through a number of vectors. yet the
   remediation advice is likely to be quite different and may or may not
   be directly serviceable by the Internet user.  Diligence needs to be
   taken by the ISP in understanding the specific nature of the device
   that has been infected with a bot, and providing appropriate
   remediation advice.

5.4.  Guided Remediation Process

   Minimally the Guided Remediation Process should include options
   and/or recommendations on how a user should:

   1.  Backup personal Documents, for example: "Before you start, make
       sure to back up all of your important data.  (You should do this
       on a regular basis anyway.)  You can back up your files manually
       or using a system back-up software utility, which may be part of
       your Operating System (OS).  You can back your files up to a USB
       Thumb Drive (aka USB Key), a CD/DVD-ROM, an external hard drive,
       or a network file server."

   2.  Download OS patches and Anti-Virus (A/V) software updates.  For
       example, links could be provided to Microsoft Windows updates at
       default.aspx?ln=en-us as well as to Apple MacOS updates at

   3.  Explain how to configure the computer to automatically install
       updates for the OS, A/V and other common Web Browsers such as
       Microsoft Internet Explorer, Mozilla Firefox, Apple Safari,
       Opera, and Google Chrome.

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   4.  The flow should also have the option for users to get
       professional assistance if they are unable to remove the bots
       themselves.  If purchasing third party assistance, then the user
       should be encouraged to pre-determine how much they are willing
       to pay for that help.  If the computer that is being remediated
       is old and can easily be replaced with a new, faster, larger and
       more reliable system for three or four hundred dollars, the it
       makes no sense to spend five or six hundred dollars to fix the
       old computer, for example.  On the other hand, if the customer
       has a brand new computer that cost several thousand dollars, it
       might make perfect sense to spend the money in attempting to
       remediate it.

   5.  To continue, regardless of whether the user or a knowledgeable
       technical assistant is working on remediating the computer, their
       first task should be to determine which of multiple potentially-
       infected machines may be the one that needs attention (in the
       common case of multiple computers in a home network).  Sometimes,
       as in cases where there is only a single directly-attached
       computer, or the user has been noticing problems with one of
       their computers, this can be easy.  Other times, it may be more
       difficult.  If the user is behind a home gateway/router, then the
       first task may be to ascertain which of the machines is infected.
       In some cases the user may have to check all machines to identify
       the infected one.

   6.  User surveys to solicit feedback on whether the notification and
       remediation process is effective and what recommended changes
       could be made in order to improve the ease, understandability,
       and effectiveness the remediation process.

   7.  If the user is interested in reporting his or her computer's bot
       infection to an applicable law enforcement authority, then the
       computer effectively becomes a cyber "crime scene" and should not
       be mitigated unless or until law enforcement has collected the
       necessary evidence.  For individuals in this situation, the ISP
       should refer them to local, state, federal, or other relevant
       computer crime offices.  (Note: Some "minor" incidents, even if
       highly traumatic to the user, may not be sufficiently serious for
       law enforcement to commit some of their limited resources to an

6.  Security Considerations

   There are no security considerations to include at this time.

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7.  IANA Considerations

   There are no IANA considerations in this document.

8.  Acknowledgements

   The authors wish to acknowledge the following individuals and
   organisations for their review and feedback of this document:

   Jonathan Curtis

   Jeff Chan

   Roland Dobbins

   Eliot Gillum

   Messaging Anti-Abuse Working Group (MAAWG)

   Jose Nazario

   Gunter Ollmann

   Eric Ziegast

9.  Informative references

   [RFC1459]  Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol",
              RFC 1459, May 1993.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

              FUNCTIONS", RFC 2142, May 1997.

   [RFC3954]  Claise, B., "Cisco Systems NetFlow Services Export Version
              9", RFC 3954, October 2004.

Appendix A.  Document Change Log

   [RFC Editor: This section is to be removed before publication]

   -01 version:

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   o  -01 version published

Appendix B.  Open Issues

   [RFC Editor: This section is to be removed before publication]

   Could use some informational references in Section 3

   Fix the odd list spacing in Section 5.1

   Consider revision of the OS update links, to simplify them.

   Add some point about notification to large networks may not be useful
   -- such as coffee shops or hotels with WiFi networks.

Authors' Addresses

   Jason Livingood
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103


   Nirmal Mody
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103


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   Mike O'Reirdan
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103


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