Internet Engineering Task Force J. Livingood
Internet-Draft N. Mody
Intended status: Informational M. O'Reirdan
Expires: August 12, 2010 Comcast
February 8, 2010
Recommendations for the Remediation of Bots in ISP Networks
draft-oreirdan-mody-bot-remediation-04
Abstract
This document contains recommendations on how Internet Service
Providers can manage the effects of computers used by their
subscribers, which have been infected with malicious bots, via
various remediation techniques. Internet users with infected
computers are exposed to risks such as loss of personal data, as well
as increased susceptibility to online fraud and/or phishing. Such
computers can also become an inadvertent participant in or component
of an online crime network, spam network, and/or phishing network, as
well as be used as a part of a distributed denial of service attack.
Mitigating the effects of and remediating the installations of
malicious bots 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 Internet Service Provider's network.
Status of this Memo
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This Internet-Draft will expire on August 12, 2010.
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Copyright Notice
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Table of Contents
1. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
2. Key Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
3. Introduction and Problem Statement . . . . . . . . . . . . . . 6
4. Important Notice of Limitations and Scope . . . . . . . . . . 7
5. Detection of Bots . . . . . . . . . . . . . . . . . . . . . . 7
6. Notification to Internet Users . . . . . . . . . . . . . . . . 11
7. Remediation of Compters Infected with a Bot . . . . . . . . . 16
8. Guided Remediation Process . . . . . . . . . . . . . . . . . . 17
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
12. Informative references . . . . . . . . . . . . . . . . . . . . 20
Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 20
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Key Terminology
This section defines the key terms used in this document.
2.1. Malicious Bots, or Bots
A malicious "bot" (derived from the word "robot", hereafter simply
referred to as a "bot") 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', or benign 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 can be 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, distributed denial of service (DDoS)
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
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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. Newer
command and control methods have evolved, such that those currently
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
refer to a computing device that connects to the Internet. This
encompasses devices used 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 to 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, such as may be the
case with various smart home and smart grid devices.
2.4. Malware
This is short for malicious software. In this case, malicious bots
are considered a subset of malware. Other forms of malware could
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-connected computers may become infected with
malware through externally initiated malicious activities such as the
exploitation of vulnerabilities or the brute force guessing of access
credentials.
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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.
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 and 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 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.
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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
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.
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, as described later in this document.
4. Important Notice of Limitations and Scope
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 in a state
where it is 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. Experienced users would have to reflash BIOS in
their machines in order to remove BIOS-based malware.
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, infected by bots in the future.
5. Detection of Bots
An ISP must first identify that an Internet user, in this case a user
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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
privacy of the personally identifiable information (PII) 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 and end-user applications.
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 as one particular type of bot need to be continuously
monitored and tracked in order to correctly identify the threat they
pose at any particular point in time.
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 may cause some 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
'definitive-vs-likely' challenge is difficult and, when in doubt,
ISPs should probably err on the side of caution by communicating when
a likely bot infection has taken place. 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
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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' PII is maintained. While bot detection
methods, tools, and processes are similar to spam and virus defenses
deployed by the ISP for the benefit 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 any PII
collected or incidentally detected is properly protected. The
definition of PII varies from one jurisdiction to the next so proper
care must be taken to ensure that any actions taken comply with
legislation and good practice in the jurisdiction in which the PII is
gathered. 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, evolving
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
networks.
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.
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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
(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 the DSHIELD AS tool from the SANS Institue.
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 a DDoS attack because computers participating in the
attack will likely be infected by a bot, frequently as observed
at network borders.
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.
e. User complaints: Because hosts infected by bots 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.
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g. ISPs may operate or subscribe to services that provide
'sinkholing' or 'honeynet' capabilities. This may enable the ISP
to obtain near-real-time lists of bot infected computers as they
attempt to join a larger botnet or propagate to other hosts on a
network.
h. ISP industry associations should examine the possiblity of
collating statistics from ISP members in order to provide good
statistics about bot infections based on real ISP data.
i. An Intrusion Detection System(IDS) can be a useful tool to
actually identify to help identify the malware. An IDS tool such
as SNORT (open source IDS platform) can be placed in a Walleed
Garden and used to analyse end user traffic to confirm malware
type. This will help with remediation of the infected device.
6. 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 should 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, and that each has its own set of limitations. In
addition, in some cases, an 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 of time which is necessary, in order to maintain the
protection of the privacy of an individual subscriber.
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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.
6.1. 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 method in which to request or retain the primary email
addresses of Internet users of their networks. Another possibility
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, generally referred to as 'phishing', 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.
6.2. 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 calls, 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 to a
user, that user is very likely to lack the necessary technical
expertise to understand or be able to effectively deal with the
threat.
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6.3. Postal Mail Notification
This form of notification is probably the least popular and effective
means of communication, due to both preparation time, delivery time,
the cost of printing and paper, and the cost of postage.
6.4. 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.
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 example, a user could be playing a game online, via the use of
a dedicated, Internet-connected game console. In another example,
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
perspective.
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 may also involve a 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
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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). In
such a case, 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.
Finally, when a walled garden is used, a list of well-known addresses
for both operating system vendors and security vendors should be
created and maintained in a white list which permits access to these
sites. This can be important for allowing access from the walled
garden by end users in search of operating system and application
patches.
6.5. Instant Message Notification
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 a cost effective means to communicate with users
automatically from an IM alert system or via a manual process, by the
ISP's support staff. Ideally, the ISP should allow the user to
register their IM identity in an ISP account management system and
grant permission to be contacted via this means. If the IM service
provider supports off-line messaging, then the user can be notified
regardless of whether they are currently logged into the IM system.
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. Also, 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. Even in those cases where a user
does have an IM address, they may not be signed onto that IM system
when the notification is attempted. There maybe also be a privacy
concern on the part of users, when such an IM notification must be
transmitted over a third-party network and/or IM service. As such,
should this method be used, the notification should be discreet and
not include any PII in the notification itself.
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6.6. Short Message Service (SMS) Notification
SMS allows the ISP send a brief description of the problem to notify
the user of the issue, typically to a mobile device such as a mobile
phone or smart phone. Ideally, the ISP should allow the user to
register their mobile number and/or SMS address in an ISP account
management system and grant permission to be contacted via this
means. The primary advantage of SMS is that users are familiar with
receiving text messages and are likely to read them. However, users
may not act on the notification immediately if they are not in front
of their computer system at the time of the SMS notification.
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, given constraints on the number of
characters in an individual message (typically 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 network service providers or use a third-party SMS
clearinghouse (relay) to notify users. In both cases, an ISP will
typically pay on a per-message basis to send SMS notifications. An
additional downside is that SMS messages sent to a user may result in
a charge to the user by their wireless provider, depending upon the
plat to which they subscribe. Another minor disadvantage is that it
is possible to notify the wrong user if the intended user changes
their mobile number but forgets to update it with the ISP.
There are several other drawbacks with this communications method.
There is a high probability that subscriber may interpret the
communication to be spam, and as such ignore it. Also, not every
user uses SMS and/or the user may not provide their SMS address or
mobile number to the ISP. Even in those cases where a user does have
an SMS address or mobile number, their device may not be powered on
or otherwise available on a wireless network when the notification is
attempted. There maybe also be a privacy concern on the part of
users, when such an SMS notification must be transmitted over a
third-party network and/or SMS clearinghouse. As such, should this
method be used, the notification should be discreet and not include
any PII in the notification itself.
6.7. 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
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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, VoIP calls, etc.
(as noted in Section 6.4).
7. Remediation of Compters Infected with a Bot
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
may provide some recommended means to clean the computer. The
generally recommended approach is to provide the necessary tools and
education to the user so that they may perform bot remediation
themselves, particularly given the risks and difficulties inherent in
attempting to remove a bot.
For example, this may include the creation of a special web site with
security-oriented content that is dedicated for this purpose. This
should be a well-publicized security web site to which a user with a
bot infection can be directed to for remediation. This security web
site 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 attempt to clean their computer and provide
information on how users can keep the computer free of future
infections. The security web site should also have a guided process
that takes non-technical users through the remediation process, on an
easily understood, step-by-step basis.
In terms of the text used to explain what bots are and the threats
that 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 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
information."
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It is also important to note that it may not be immediately apparent
to the Internet user precisely which devices have been infected with
a particular bot. This may be due to the user's home network
configuration, which may encompass several computers, where a home
gateway which performs Network Address Translation (NAT) to share a
single public IP address has been used. Therefore, any of these
devices can be infected with a bot. The consequence of this for an
ISP is that remediation advice may not ultimately be immediately
actionable by the Internet user, as that user may need to perform
additional investigation within their own home network.
An added complication is that the user may have a bot infection on a
device such as a video console, multimedia system, appliance, or
other end-user computing device which does not have a typical Windows
or Macintosh user interface. As a result, diligence needs to be
taken by the ISP where possible such that they can identify and
communicate the specific nature of the device that has been infected
with a bot, and further providing appropriate remediation advice.
There are a number of forums that exist online to provide security
related support to end users. These forums are staffed by volunteers
and often are focussed around the use of a common tool set to help
end users to remediate computers infected with malware. It may be
advantageous to ISPs to foster a relationship with one or more
forums, perhaps by offering free hosting or other forms of
sponsorship.
8. 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
http://update.microsoft.com/microsoftupdate/v6/
default.aspx?ln=en-us as well as to Apple MacOS updates at
http://support.apple.com/kb/HT1338?viewlocale=en_US.
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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.
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
investigation.)
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9. Security Considerations
This document describes in detail the numerous security risks and
concerns relating to bot nets. As such, it has been appropriate to
include specific information about security in each section above.
This document describes the security risks related to malicious bot
infections themselves, such as enabling identity theft, theft of
authentication credentials, and the use of a computer to unwittingly
participate in a DDoS attack, among many other risks. This document
also describes at a high level the activities that ISPs should be
sensitive to, where the collection or communication of PII may be
possible. Finally, the document also describes security risks which
may relate to the particular methods of communicating a notification
to Internet users. Bot networks and bot infections pose extremely
serious security risks and any reader should review this document
carefully.
10. IANA Considerations
There are no IANA considerations in this document.
11. 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
The Messaging Anti-Abuse Working Group (MAAWG)
Jose Nazario
Gunter Ollmann
Joe Stewart
Eric Ziegast
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12. 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.
[RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND
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]
-04 version:
o Updated reference to BIOS based malware, added wording on PII and
local jurisdictions, added suggestion that industry body produce
bot stats, added suggestion that ISPs use volunteer forums
-03 version:
o all updates from Jason - now ready for wider external review
-02 version:
o all updates from Jason - still some open issues but we're now at a
place where we can solicit more external feedback
-01 version:
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
Consider revision of the OS update links, to simplify them.
Add some point about notification to large networks may not be useful
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-- 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
US
Email: jason_livingood@cable.comcast.com
URI: http://www.comcast.com
Nirmal Mody
Comcast Cable Communications
One Comcast Center
1701 John F. Kennedy Boulevard
Philadelphia, PA 19103
US
Email: nirmal_mody@cable.comcast.com
URI: http://www.comcast.com
Mike O'Reirdan
Comcast Cable Communications
One Comcast Center
1701 John F. Kennedy Boulevard
Philadelphia, PA 19103
US
Email: michael_oreirdan@cable.comcast.com
URI: http://www.comcast.com
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