rfc4948
Network Working Group L. Andersson
Request for Comments: 4948 Acreo AB
Category: Informational E. Davies
Folly Consulting
L. Zhang
UCLA
August 2007
Report from the IAB workshop on Unwanted Traffic March 9-10, 2006
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document reports the outcome of a workshop held by the Internet
Architecture Board (IAB) on Unwanted Internet Traffic. The workshop
was held on March 9-10, 2006 at USC/ISI in Marina del Rey, CA, USA.
The primary goal of the workshop was to foster interchange between
the operator, standards, and research communities on the topic of
unwanted traffic, as manifested in, for example, Distributed Denial
of Service (DDoS) attacks, spam, and phishing, to gain understandings
on the ultimate sources of these unwanted traffic, and to assess
their impact and the effectiveness of existing solutions. It was
also a goal of the workshop to identify engineering and research
topics that could be undertaken by the IAB, the IETF, the IRTF, and
the network research and development community at large to develop
effective countermeasures against the unwanted traffic.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Root of All Evils: An Underground Economy . . . . . . . . 4
2.1. The Underground Economy . . . . . . . . . . . . . . . . . 5
2.2. Our Enemy Using Our Networks, Our Tools . . . . . . . . . 6
2.3. Compromised Systems Being a Major Source of Problems . . . 7
2.4. Lack of Meaningful Deterrence . . . . . . . . . . . . . . 8
2.5. Consequences . . . . . . . . . . . . . . . . . . . . . . . 10
3. How Bad Is The Problem? . . . . . . . . . . . . . . . . . . . 10
3.1. Backbone Providers . . . . . . . . . . . . . . . . . . . . 10
3.1.1. DDoS Traffic . . . . . . . . . . . . . . . . . . . . . 10
3.1.2. Problem Mitigation . . . . . . . . . . . . . . . . . . 11
3.2. Access Providers . . . . . . . . . . . . . . . . . . . . . 12
3.3. Enterprise Networks: Perspective from a Large
Enterprise . . . . . . . . . . . . . . . . . . . . . . . . 13
3.4. Domain Name Services . . . . . . . . . . . . . . . . . . . 14
4. Current Vulnerabilities and Existing Solutions . . . . . . . . 15
4.1. Internet Vulnerabilities . . . . . . . . . . . . . . . . . 15
4.2. Existing Solutions . . . . . . . . . . . . . . . . . . . . 16
4.2.1. Existing Solutions for Backbone Providers . . . . . . 16
4.2.2. Existing Solutions for Enterprise Networks . . . . . . 17
4.3. Shortfalls in the Existing Network Protection . . . . . . 18
4.3.1. Inadequate Tools . . . . . . . . . . . . . . . . . . . 18
4.3.2. Inadequate Deployments . . . . . . . . . . . . . . . . 18
4.3.3. Inadequate Education . . . . . . . . . . . . . . . . . 19
4.3.4. Is Closing Down Open Internet Access Necessary? . . . 19
5. Active and Potential Solutions in the Pipeline . . . . . . . . 20
5.1. Central Policy Repository . . . . . . . . . . . . . . . . 20
5.2. Flow Based Tools . . . . . . . . . . . . . . . . . . . . . 21
5.3. Internet Motion Sensor (IMS) . . . . . . . . . . . . . . . 21
5.4. BCP 38 . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.5. Layer 5 to 7 Awareness . . . . . . . . . . . . . . . . . . 22
5.6. How To's . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.7. SHRED . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6. Research in Progress . . . . . . . . . . . . . . . . . . . . . 23
6.1. Ongoing Research . . . . . . . . . . . . . . . . . . . . . 23
6.1.1. Exploited Hosts . . . . . . . . . . . . . . . . . . . 23
6.1.2. Distributed Denial of Service (DDoS) Attacks . . . . . 25
6.1.3. Spyware . . . . . . . . . . . . . . . . . . . . . . . 26
6.1.4. Forensic Aids . . . . . . . . . . . . . . . . . . . . 26
6.1.5. Measurements . . . . . . . . . . . . . . . . . . . . . 27
6.1.6. Traffic Analysis . . . . . . . . . . . . . . . . . . . 27
6.1.7. Protocol and Software Security . . . . . . . . . . . . 27
6.2. Research on the Internet . . . . . . . . . . . . . . . . . 27
6.2.1. Research and Standards . . . . . . . . . . . . . . . . 28
6.2.2. Research and the Bad Guys . . . . . . . . . . . . . . 29
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7. Aladdin's Lamp . . . . . . . . . . . . . . . . . . . . . . . . 30
7.1. Security Improvements . . . . . . . . . . . . . . . . . . 30
7.2. Unwanted Traffic . . . . . . . . . . . . . . . . . . . . . 31
8. Workshop Summary . . . . . . . . . . . . . . . . . . . . . . . 31
8.1. Hard Questions . . . . . . . . . . . . . . . . . . . . . . 31
8.2. Medium or Long Term Steps . . . . . . . . . . . . . . . . 32
8.3. Immediately Actionable Steps . . . . . . . . . . . . . . . 33
9. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 33
10. Security Considerations . . . . . . . . . . . . . . . . . . . 38
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 38
12. Informative References . . . . . . . . . . . . . . . . . . . . 39
Appendix A. Participants in the Workshop . . . . . . . . . . . . 40
Appendix B. Workshop Agenda . . . . . . . . . . . . . . . . . . . 41
Appendix C. Slides . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction
The Internet carries a lot of unwanted traffic today. To gain a
better understanding of the driving forces behind such unwanted
traffic and to assess existing countermeasures, the IAB organized an
"Unwanted Internet Traffic" workshop and invited experts on different
aspects of unwanted traffic from operator, vendor, and research
communities to the workshop. The intention was to share information
among people from different fields and organizations, fostering an
interchange of experiences, views, and ideas between the various
communities on this important topic. The major goal of this workshop
was to stimulate discussion at a deep technical level to assess
today's situation in regards to:
o the kinds of unwanted traffic that are seen on the Internet,
o how bad the picture looks,
o who and where are the major sources of the problem,
o which solutions work and which do not, and
o what needs to be done.
The workshop was very successful. Over one and half days of
intensive discussions, the major sources of the unwanted traffic were
identified, and a critical assessment of the existing mitigation
tools was conducted. However, due to the limitation of available
time, it was impossible to cover the topic of unwanted traffic in its
entirety. Thus, for some of the important issues, only the surface
was touched. Furthermore, because the primary focus of the workshop
was to collect and share information on the current state of affairs,
it is left as the next step to attempt to derive solutions to the
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issues identified. This will be done in part as activities within
the IAB, the IETF, and the IRTF.
During the workshop, a number of product and company names were
cited, which are reflected in the report to a certain extent.
However, a mention of any product in this report should not be taken
as an endorsement of that product; there may well be alternative,
equally relevant or efficacious products in the market place.
This report is a summary of the contributions by the workshop
participants, and thus it is not an IAB document. The views and
positions documented in the report do not necessarily reflect IAB
views and positions.
The workshop participant list is attached in Appendix A. The agenda
of the workshop can be found in Appendix B. Links to a subset of the
presentations are provided in Appendix C; the rest of the
presentations are of a sensitive nature, and it has been agreed that
they will not be made public. Definitions of the jargon used in
describing unwanted traffic can be found in Section 9.
2. The Root of All Evils: An Underground Economy
The first important message this workshop would like to bring to the
Internet community's attention is the existence of an underground
economy. This underground economy provides an enormous amount of
monetary fuel that drives the generation of unwanted traffic. This
economic incentive feeds on an Internet that is to a large extent
wide open. The open nature of the Internet fosters innovations but
offers virtually no defense against abuses. It connects to millions
of mostly unprotected hosts owned by millions of mostly naive users.
These users explore and benefit from the vast opportunities offered
by the new cyberspace, with little understanding of its vulnerability
to abuse and the potential danger of their computers being
compromised. Moreover, the Internet was designed without built-in
auditing trails. This was an appropriate choice at the time, but now
the lack of traceability makes it difficult to track down malicious
activities. Combined with a legal system that is yet to adapt to the
new challenge of regulating the cyberspace, this means the Internet,
as of today, has no effective deterrent to miscreants. The
unfettered design and freedom from regulation have contributed to the
extraordinary success of the Internet. At the same time, the
combination of these factors has also led to an increasing volume of
unwanted traffic. The rest of this section provides a more detailed
account of each of the above factors.
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2.1. The Underground Economy
As in any economic system, the underground economy is regulated by a
demand and supply chain. The underground economy, which began as a
barter system, has evolved into a giant shopping mall, commonly
running on IRC (Internet Relay Chat) servers. The IRC servers
provide various online stores selling information about stolen credit
cards and bank accounts, malware, bot code, botnets, root accesses to
compromised hosts and web servers, and much more. There are DDoS
attack stores, credit card stores, PayPal and bank account stores, as
well as Cisco and Juniper router stores that sell access to
compromised routers. Although not everything can be found on every
server, most common tools used to operate in the underground economy
can be found on almost all the servers.
How do miscreants turn attack tools and compromised machines into
real assets? In the simplest case, miscreants electronically
transfer money from stolen bank accounts directly to an account that
they control, often in another country. In a more sophisticated
example, miscreants use stolen credit cards or PayPal accounts for
online purchases. To hide their trails, they often find remailers
who receive the purchased goods and then repackage them to send to
the miscreants for a fee. The miscreants may also sell the goods
through online merchandising sites such as eBay. They request the
payments be made in cashier checks or money orders to be sent to the
people who provide money laundering services for the miscreants by
receiving the payments and sending them to banks in a different
country, again in exchange for a fee. In either case, the
destination bank accounts are used only for a short period and are
closed as soon as the money is withdrawn by the miscreants.
The miscreants obtain private and financial information from
compromised hosts and install bots (a.k.a. zombies) on them. They
can also obtain such information from phishing attacks. Spam
messages mislead naive users into accessing spoofed web sites run by
the miscreants where their financial information is extracted and
collected.
The miscreants in general are not skilled programmers. With money,
however, they can hire professional writers to produce well phrased
spam messages, and hire coders to develop new viruses, worms,
spyware, and botnet control packages, thereby resupplying the
underground market with new tools that produce more unwanted traffic
on the Internet: spam messages that spread phishing attacks, botnets
that are used to launch DDoS attacks, click fraud that "earns" income
by deceiving online commercial advertisers, and new viruses and worms
that compromise more hosts and steal additional financial information
as well as system passwords and personal identity information.
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The income gained from the above illegal activities allows miscreants
to hire spammers, coders, and IRC server providers. Spammers use
botnets. Direct marketing companies set up dirty affiliate programs.
Some less than scrupulous banks are also involved to earn transaction
fees from moving the dirty money around. In the underground market,
everything can be traded, and everything has a value. Thus is
spawned unwanted traffic of all kinds.
The underground economy has evolved very rapidly over the past few
years. In the early days of bots and botnets, their activities were
largely devoted to DDoS attacks and were relatively easy to detect.
As the underground economy has evolved, so have the botnets. They
have moved from easily detectable behavior to masquerading as normal
user network activity to achieve their goals, making detection very
difficult even by vigilant system administrators.
The drive for this rapid evolution comes to a large extent from the
change in the intention of miscreant activity. Early virus attacks
and botnets were largely anarchic activities. Many were done by
"script kiddies" to disrupt systems without a real purpose or to
demonstrate the prowess of the attacker, for example in compromising
systems that were touted as "secure". Mirroring the
commercialization of the Internet and its increasing use for
e-business, miscreant activity is now mostly focused on conventional
criminal lines. Systems are quietly subverted with the goal of
obtaining illicit financial gain in the future, rather than causing
visible disruptions as was often the aim of the early hackers.
2.2. Our Enemy Using Our Networks, Our Tools
Internet Relay Chat (IRC) servers are commonly used as the command
and control channel for the underground market. These servers are
paid for by miscreants and are professionally supported. They are
advertised widely to attract potential consumers, and thus are easy
to find. The miscreants first talk to each other on the servers to
find out who is offering what on the market, then exchange encrypted
private messages to settle the deals.
The miscreants are not afraid of network operators seeing their
actions. If their activities are interrupted, they simply move to
another venue. When ISPs take actions to protect their customers,
revenge attacks are uncommon as long as the miscreants' cash flow is
not disturbed. When a botnet is taken out, they move on to the next
one, as there is a plentiful supply. However, if an IRC server is
taken out that disturbs their cash flow, miscreants can be ruthless
and severe attacks may follow. They currently have no fear, as they
know the chances of their being caught are minimal.
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Our enemies make good use of the Internet's global connectivity as
well as all the tools the Internet has developed. IRC servers
provide a job market for the miscreants and shopping malls of attack
tools. Networking research has produced abundant results making it
easier to build large scale distributed systems, and these have been
adopted by miscreants to build large size, well-controlled botnets.
Powerful search engines also enable one to quickly find readily
available tools and resources. The sophistication of attacks has
increased with time, while the skills required to launch effective
attacks have become minimal. Attackers can be hiding anywhere in the
Internet while attacks get launched on a global scale.
2.3. Compromised Systems Being a Major Source of Problems
The current Internet provides a field ripe for exploitation. The
majority of end hosts run vulnerable platforms. People from all
walks of life eagerly jump into the newly discovered online world,
yet without the proper training needed to understand the full
implications. This is at least partially due to most users failing
to anticipate how such a great invention can be readily abused. As a
result, the Internet has ended up with a huge number of compromised
hosts, without their owners being aware that it has happened.
Unprotected hosts can be compromised in multiple ways. Viruses and
worms can get into the system through exploiting bugs in the existing
operating systems or applications, sometimes even in anti-virus
programs. A phishing site may also take the opportunity to install
malware on a victim's computer when a user is lured to the site.
More recently, viruses have also started being propagated through
popular peer-to-peer file sharing applications. With multiple
channels of propagation, malware has become wide-spread, and infected
machines include not only home PCs (although they do represent a
large percentage), but also corporate servers, and even government
firewalls.
News of new exploits of vulnerabilities of Microsoft Windows
platforms is all too frequent, which leads to a common perception
that the Microsoft Windows platform is a major source of
vulnerability. One of the reasons for the frequent vulnerability
exploits of the Windows system is its popularity in the market place;
thus, a miscreant's investment in each exploit can gain big returns
from infecting millions of machines. As a result, each incident is
also likely to make headlines in the news. In reality, all other
platforms such as Linux, Solaris, and MAC OS for example, are also
vulnerable to compromises. Routers are not exempt from security
break-ins either, and using a high-end router as a DoS launchpad can
be a lot more effective than using a bundle of home PCs.
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Quietly subverting large numbers of hosts and making them part of a
botnet, while leaving their normal functionality and connectivity
essentially unimpaired, is now a major aim of miscreants and it
appears that they are being all too successful. Bots and the
functions they perform are often hard to detect and most of the time
their existence are not known to system operators or owners (hence,
the alternative name for hosts infected with bots controlled by
miscreants - zombies); by the time they are detected, it might very
well be too late as they have carried out the intended
(mal-)function.
The existence of a large number of compromised hosts is a
particularly challenging problem to the Internet's security. Not
only does the stolen financial information lead to enormous economic
losses, but also there has been no quick fix to the problem. As
noted above, in many cases the owners of the compromised computers
are unaware of the problem. Even after being notified, some owners
still do not care about fixing the problem as long as their own
interest, such as playing online games, is not affected, even though
the public interest is endangered --- large botnets can use multi-
millions of such compromised hosts to launch DDoS attacks, with each
host sending an insignificant amount of traffic but the aggregate
exceeding the capacity of the best engineered systems.
2.4. Lack of Meaningful Deterrence
One of the Internet's big strengths is its ability to provide
seamless interconnection among an effectively unlimited number of
parties. However, the other side of the same coin is that there may
not be clear ways to assign responsibilities when something goes
wrong. Taking DDoS attacks as an example, an attack is normally
launched from a large number of compromised hosts, the attack traffic
travels across the Internet backbone to the access network(s) linking
to the victims. As one can see, there are a number of independent
stake-holders involved, and it is not immediately clear which party
should take responsibility for resolving the problem.
Furthermore, tracking down an attack is an extremely difficult task.
The Internet architecture enables any IP host to communicate with any
other hosts, and it provides no audit trails. As a result, not only
is there no limit to what a host may do, but also there is no trace
after the event of what a host may have done. At this time, there is
virtually no effective tool available for problem diagnosis or packet
trace back. Thus, tracking down an attack is labor intensive and
requires sophisticated skills. As will be mentioned in the next
section, there is also a lack of incentive to report security
attacks. Compounded with the high cost, these factors make forensic
tracing of an attack to its root a rare event.
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In human society, the legal systems provide protection against
criminals. However, in the cyberspace, the legal systems are lagging
behind in establishing regulations. The laws and regulations aim at
penalizing the conduct after the fact. If the likelihood of
detection is low, the deterrence would be minimal. Many national
jurisdictions have regulations about acts of computer fraud and
abuse, and they often carry significant criminal penalties. In the
US (and many other places), it is illegal to access government
computers without authorization, illegal to damage protected
government computers, and illegal to access confidential information
on protected computers. However, the definition of "access" can be
difficult to ascertain. For example, is sending an ICMP (Internet
Control Messaging Protocol) packet to a protected computer considered
illegal access? There is a lack of technical understanding among
lawmakers that would be needed to specify the laws precisely and
provide effective targeting limited to undesirable acts. Computer
fraud and liabilities laws provide a forum to address illegal access
activities and enable prosecution of cybercriminals. However, one
difficulty in prosecuting affiliate programs using bot infrastructure
is that they are either borderline legal, or there is little
evidence. There is also the mentality of taking legal action only
when the measurable monetary damage exceeds a high threshold, while
it is often difficult to quantify the monetary damage in individual
cases of cyberspace crimes.
There is a coalition between countries on collecting cybercriminal
evidence across the world, but there is no rigorous way to trace
across borders. Laws and rules are mostly local to a country,
policies (when they exist) are mostly enacted and enforced locally,
while the Internet itself, that carries the unwanted traffic,
respects no borders. One estimate suggests that most players in the
underground economy are outside the US, yet most IRC servers
supporting the underground market may be running in US network
providers, enjoying the reliable service and wide connectivity to the
rest of the world provided by the networks.
In addition, the definition of "unwanted" traffic also varies between
different countries. For example, China bans certain types of
network traffic that are considered legitimate elsewhere. Yet
another major difficulty is the trade-off and blurred line between
having audit trails to facilitate forensic analysis and to enforce
censorship. The greater ability we build into the network to control
traffic, the stronger would be the monitoring requirements coming
from the legislators.
It should be emphasized that, while a legal system is necessary to
create effective deterrence and sanctions against miscreants, it is
by no means sufficient on its own. Rather, it must be accompanied by
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technical solutions to unwanted traffic detection and damage
recovery. It is also by no means a substitute for user education.
Only a well informed user community can collectively establish an
effective defense in the cyberspace.
2.5. Consequences
What we have today is not a rosy picture: there are
o big economic incentives and a rich environment to exploit,
o no specific party to carry responsibility,
o no auditing system to trace back to the sources of attacks, and
o no well established legal regulations to punish offenders.
The combination of these factors inevitably leads to ever increasing
types and volume of unwanted traffic. However, our real threats are
not the bots or DDoS attacks, but the criminals behind them.
Unwanted traffic is no longer only aiming for maximal disruption; in
many cases, it is now a means to illicit ends with the specific
purpose of generating financial gains for the miscreants. Their
crimes cause huge economic losses, counted in multiple billions of
dollars and continuing.
3. How Bad Is The Problem?
There are quite a number of different kinds of unwanted traffic on
the Internet today; the discussions at this workshop were mainly
around DDoS traffic and spam. The impact of DDoS and spam on
different parts of the network differs. Below, we summarize the
impact on backbone providers, access providers, and enterprise
customers, respectively.
3.1. Backbone Providers
Since backbone providers' main line of business is packet forwarding,
the impact of unwanted traffic is mainly measured by whether DDoS
traffic affects network availability. Spam or malware is not a major
concern because backbone networks do not directly support end users.
Router compromises may exist, but they are rare events at this time.
3.1.1. DDoS Traffic
Observation shows that, in the majority of DDoS attacks, attack
traffic can originate from almost anywhere in the Internet. In
particular, those regions with high speed user connectivity but
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poorly managed end hosts are often the originating sites of DDoS
attacks. The miscreants tend to find targets that offer maximal
returns with minimal efforts.
Backbone networks in general are well-provisioned in regard to
traffic capacities. Therefore, core routers and backbone link
capacity do not get affected much by most DDoS attacks; a 5Gbps
attack could be easily absorbed without causing noticeable impact on
the performance of backbone networks. However, DDoS attacks often
saturate access networks and make a significant impact on customers.
In particular, multihomed customers who have multiple well-
provisioned connections for high throughput and performance may
suffer from aggregated DDoS traffic coming in from all directions.
3.1.2. Problem Mitigation
Currently, backbone networks do not have effective diagnosis or
mitigation tools against DDoS attacks. The foremost problem is a
lack of incentives to deploy security solutions. Because IP transit
services are a commodity, controlling cost is essential to surviving
the competition. Thus, any expenditure tends to require a clearly
identified return-on-investment (ROI). Even when new security
solutions become available, providers do not necessarily upgrade
their infrastructure to deploy the solutions, as security solutions
are often prevention mechanisms that may not have an easily
quantifiable ROI. To survive in the competitive environment in which
they find themselves, backbone providers also try to recruit more
customers. Thus, a provider's reputation is important. Due to the
large number of attacks and inadequate security solution deployment,
effective attacks and security glitches can be expected. However, it
is not in a provider's best interest to report all the observed
attacks. Instead, the provider's first concern is to minimize the
number of publicized security incidents. For example, a "trouble
ticket" acknowledging the problem is issued only after a customer
complains. An informal estimate suggested that only about 10% of
DDoS attacks are actually reported (some other estimates have put the
figure as low as 2%). In short, there is a lack of incentives to
either report problems or deploy solutions.
Partly as a consequence of the lack of incentive and lack of funding,
there exist few DDoS mitigation tools for backbone providers.
Network operators often work on their own time to fight the battle
against malicious attacks. Their primary mitigation tools today are
Access Control Lists (ACL) and BGP (Border Gateway Protocol) null
routes to black-hole unwanted traffic. These tools can be turned on
locally and do not require coordination across administrative
domains. When done at, or near, DDoS victims, these simple tools can
have an immediate effect in reducing the DDoS traffic volume.
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However, these tools are rather rudimentary and inadequate, as we
will elaborate in Section 4.2.1.
3.2. Access Providers
A common issue that access providers share with backbone providers is
the lack of incentive and the shortage of funding needed to deploy
security solutions. As with the situation with security incidents on
the backbone, the number of security incidents reported by access
providers is estimated to be significantly lower than the number of
the actual incidents that occurred.
Because access providers are directly connected to end customers,
they also face unique problems of their own. From the access
providers' viewpoint, the most severe impact of unwanted traffic is
not the bandwidth exhaustion, but the customer support load it
engenders. The primary impact of unwanted traffic is on end users,
and access providers must respond to incident reports from their
customers. Today, access providers are playing the role of IT help
desk for many of their customers, especially residential users.
According to some access providers, during the Microsoft Blaster worm
attack, the average time taken to handle a customer call was over an
hour. Due to the high cost of staffing the help desks, it is
believed that, if a customer calls the help desk just once, the
provider would lose the profit they would otherwise have otherwise
made over the lifetime of that customer account.
To reduce the high customer service cost caused by security breaches,
most access providers offer free security software to their
customers. It is much cheaper to give the customer "free" security
software in the hope of preventing system compromises than handling
the system break-ins after the event. However, perhaps due to their
lack of understanding of the possible security problems they may
face, many customers fail to install security software despite the
free offer from their access providers, or even when they do, they
may lack the skill needed to configure a complex system correctly.
What factors may influence how quickly customers get the security
breaches fixed? Past experience suggests the following observations:
o Notification has little impact on end user repair behavior.
o There is no significant difference in terms of repair behavior
between different industries or between business and home users.
o Users' patching behavior follows an exponential decay pattern with
a time constant of approximately 40% per month. Thus, about 40%
of computers tend to be patched very quickly when a patch is
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released, and approximately 40% of the remaining vulnerable
computers in each following month will show signs of being
patched. This leaves a few percent still unpatched after 6
months. In the very large population of Internet hosts, this
results in a significant number of hosts that will be vulnerable
for the rest of their life.
o There is a general lack of user understanding: after being
compromised, unmanaged computers may get replaced rather than
repaired, and this often results in infections occurring during
the installation process on the replacement.
3.3. Enterprise Networks: Perspective from a Large Enterprise
The operators of one big enterprise network reported their experience
regarding unwanted traffic to the workshop. Enterprises perceive
many forms of bad traffic including worms, malware, spam, spyware,
Instant Messaging (IM), peer-to-peer (P2P) traffic, and DoS.
Compared to backbone and access providers, enterprise network
operators are more willing to investigate security breaches, although
they may hesitate to pay a high price for security solutions. False
positives are very costly. Most operators prefer false negatives to
false positives. In general, enterprises prefer prevention solutions
to detection solutions.
Deliberately created unwanted traffic (as opposed to unwanted traffic
that might arise from misconfiguration) in enterprise networks can be
sorted into three categories. The first is "Nuisance", which
includes unwanted traffic such as spam and peer-to-peer file sharing.
Although there were different opinions among the workshop
participants as to whether P2P traffic should, or should not, be
considered as unwanted traffic, enterprise network operators are
concerned not only that P2P traffic represents a significant share of
the total network load, but they are also sensitive to potential
copyright infringement issues that might lead to significant
financial and legal impacts on the company as a whole. In addition,
P2P file sharing applications have also became a popular channel for
malware propagation.
The second category of unwanted traffic is labeled "Malicious", which
includes the traffic that spreads malware. This class of traffic can
be small in volume but the cost from the resulting damage can be
high. The clean up after an incident also requires highly skilled
operators.
The third category of unwanted traffic is "Unknown": it is known that
there exists a class of traffic in the network that can be best
described in this way, as no one knows its purpose or the locations
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of the sources. Malicious traffic can be obscured by encryption,
encapsulation, or covered up as legitimate traffic. The existing
detection tools are ineffective for this type of traffic. Noisy
worms are easy to identify, but stealth worms can open a backdoor on
hosts and stay dormant for a long time without causing any noticeable
detrimental effect. This type of bad traffic has the potential to
make the greatest impact on an enterprise from a threat perspective.
There are more mitigation tools available for enterprise networks
than for backbone and access network providers; one explanation might
be the greater affordability of solutions for enterprise networks.
The costs of damage from a security breach can also have a very
significant impact on the profits of an enterprise. At the same
time, however, the workshop participants also expressed concerns
regarding the ongoing arms race between security exploits and
patching solutions. Up to now, security efforts have, by and large,
been reactive, creating a chain of security exploits and a consequent
stream of "fixes". Such a reactive mode has not only created a big
security market, but also does not enable us to get ahead of
attackers.
3.4. Domain Name Services
Different from backbone and access providers, there also exists a
class of Internet service infrastructure providers. Provision of
Domain Name System (DNS) services offers an example here. As
reported by operators from a major DNS hosting company, over time
there have been increasingly significant DDoS attacks on .com, .net
and root servers.
DNS service operators have witnessed large scale DDoS attacks. The
most recent ones include reflection attacks resulting from queries
using spoofed source addresses. The major damage caused by these
attacks are bandwidth and resource exhaustion, which led to
disruption of critical services. The peak rate of daily DNS
transactions has been growing at a much faster rate than the number
of Internet users, and this trend is expected to continue. The heavy
load on the DNS servers has led to increasing complexity in providing
the services.
In addition to intentional DDoS Attacks, some other causes of the
heavy DNS load included (1) well known bugs in a small number of DNS
servers that still run an old version of the BIND software, causing
significant load increase at top level servers; and (2)
inappropriately configured firewalls that allow DNS queries to come
out but block returning DNS replies, resulting in big adverse impacts
on the overall system. Most of such issues have been addressed in
the DNS operational guidelines drafted by the IETF DNS Operations
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Working Group; however, many DNS operators have not taken appropriate
actions.
At this time, the only effective and viable mitigation approach is
over-engineering the DNS service infrastructure by increasing link
bandwidth, the number of servers, and the server processing power, as
well as deploying network anycast. There is a concern about whether
the safety margin gained from over-engineering is, or is not,
adequate in sustaining DNS services over future attacks. Looking
forward, there are also a few new issues looming. Two imminent ones
are the expected widespread deployment of IPv6 whose new DNS software
would inevitably contain new bugs, and the DNS Security Extensions
(DNSSEC), which could potentially be abused to generate DDoS attacks.
4. Current Vulnerabilities and Existing Solutions
This section summarizes three aspects of the workshop discussions.
We first collected the major vulnerabilities mentioned in the
workshop, then made a summary of the existing solutions, and followed
up with an examination of the effectiveness, or lack of it, of the
existing solutions.
4.1. Internet Vulnerabilities
Below is a list of known Internet vulnerabilities and issues around
unwanted traffic.
o Packet source address spoofing: there has been speculation that
attacks using spoofed source addresses are decreasing, due to the
proliferation of botnets, which can be used to launch various
attacks without using spoofed source addresses. It is certainly
true that not all the attacks use spoofed addresses; however, many
attacks, especially reflection attacks, do use spoofed source
addresses.
o BGP route hijacking: in a survey conducted by Arbor Networks,
route hijacking together with source address spoofing are listed
as the two most critical vulnerabilities on the Internet. It has
been observed that miscreants hijack bogon prefixes for spam
message injections. Such hijacks do not affect normal packet
delivery and thus have a low chance of being noticed.
o Everything over HTTP: port scan attacks occur frequently in
today's Internet, looking for open TCP or UDP ports through which
to gain access to computers. The reaction from computer system
management has been to close down all the unused ports, especially
in firewalls. One result of this reaction is that application
designers have moved to transporting all data communications over
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HTTP to avoid firewall traversal issues. Transporting "everything
over HTTP" does not block attacks but has simply moved the
vulnerability from one place to another.
o Everyone comes from Everywhere: in the earlier life of the
Internet it had been possible to get some indication of the
authenticity of traffic from a specific sender based for example
on the Time To Live (TTL). The TTL would stay almost constant
when traffic from a certain sender to a specific host entered an
operators network, since the sender will "always" set the TTL to
the same value. If a change in the TTL value occurred without an
accompanying change in the routing, one could draw the conclusion
that this was potential unwanted traffic. However, since hosts
have become mobile, they may be roaming within an operator's
network and the resulting path changes may put more (or less) hops
between the source and the destination. Thus, it is no longer
possible to interpret a change in the TTL value, even if it occurs
without any corresponding change in routing, as an indication that
the traffic has been subverted.
o Complex Network Authentication: Network authentication as it is
used today is far too complex to be feasible for users to use
effectively. It will also be difficult to make it work with new
wireless access technologies.
A possible scenario envisages a customers handset that is
initially on a corporate wireless network. If that customer
steps out of the corporate building, the handset may get
connected to the corporate network through a GPRS network. The
handset may then roam to a wireless LAN network when the user
enters a public area with a hotspot. Consequently, we need
authentication tools for cases when the underlying data link
layer technology changes quickly, possibly during a single
application session.
o Unused Security Tools: Vendors and standards have produced quite a
number of useful security tools; however, not all, or even most,
of them get used extensively.
4.2. Existing Solutions
4.2.1. Existing Solutions for Backbone Providers
Several engineering solutions exist that operators can deploy to
defend the network against unwanted traffic. Adequate provisioning
is one commonly used approach that can diminish the impact of DDoS on
the Internet backbone. The solution that received most mentions at
the workshop was BCP 38 on ingress filtering: universal deployment of
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BCP 38 can effectively block DDoS attacks using spoofed source IP
addresses. At present, Access Control List (ACL) and BGP null
routing are the two tools most commonly used by network operators to
mitigate DDoS attacks. They are effective in blocking DDoS attacks,
especially when being applied at or near a victim's site.
Unfortunately, BCP 38 is not widely deployed today. BCP 38 may
require device upgrades, and is considered tedious to configure and
maintain. Although widespread deployment of BCP 38 could benefit the
Internet as a whole, deployment by individual sites imposes a certain
amount of cost to the site, and does not provide a direct and
tangible benefit in return. In other words, BCP 38 suffers from a
lack of deployment incentives.
Both BGP null routing and ACL have the drawback of relying on manual
configuration and thus are labor intensive. In addition, they also
suffer from blocking both attack and legitimate packets. There is
also a potential that some tools could back-fire, e.g., an overly
long ACL list might significantly slow down packet forwarding in a
router.
Unicast Reverse Path Filtering (uRPF), which is available on some
routers, provides a means of implementing a restricted form of BCP 38
ingress filtering without the effort of maintaining ACLs. uRPF uses
the routing table to check that a valid path back to the source
exists. However, its effectiveness depends on the specificity of the
routes against which source addresses are compared. The prevalence
of asymmetric routing means that the strict uRPF test (where the
route to the source must leave from the same interface on which the
packet being tested arrived) may have to be replaced by the loose
uRPF test (where the route may leave from any interface). The loose
uRPF test is not a guarantee against all cases of address spoofing,
and it may still be necessary to maintain an ACL to deal with
exceptions.
4.2.2. Existing Solutions for Enterprise Networks
A wide variety of commercial products is available for enterprise
network protection. Three popular types of protection mechanisms are
o Firewalls: firewalls are perhaps the most widely deployed
protection products. However, the effectiveness of firewalls in
protecting enterprise confidential information can be weakened by
spyware installed internally, and they are ineffective against
attacks carried out from inside the perimeter established by the
firewalls. Too often, spyware installation is a byproduct of
installing other applications permitted by end users.
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o Application level gateways: these are becoming more widely used.
However, because they require application-specific support, and in
many cases they cache all the in-flight documents, configuration
can be difficult and the costs high. Thus, enterprise network
operators prefer network level protections over layer-7 solutions.
o Anti-spam software: Anti-spam measures consume significant human
resources. Current spam mitigation tools include blacklists and
content filters. The more recent "learning" filters may help
significantly reduce the human effort needed and decrease the
number of both false positives and negatives.
A more recent development is computer admission control, where a
computer is granted network access if and only if it belongs to a
valid user and appears to have the most recent set of security
patches installed. It is however a more expensive solution. A major
remaining issue facing enterprise network operators is how to solve
the user vulnerability problem and reduce reliance on user's
understanding of the need for security maintenance.
4.3. Shortfalls in the Existing Network Protection
4.3.1. Inadequate Tools
Generally speaking, network and service operators do not have
adequate tools for network problem diagnosis. The current approaches
largely rely on the experience and skills of the operators, and on
time-consuming manual operations. The same is true for mitigation
tools against attacks.
4.3.2. Inadequate Deployments
The limited number of existing Internet protection measures have not
been widely deployed. Deployment of security solutions requires
resources which may not be available. It also requires education
among the operational community to recognize the critical importance
of patch installation and software upgrades; for example, a bug in
the BIND packet was discovered and fixed in 2003, yet a number of DNS
servers still run the old software today. Perhaps most importantly,
a security solution must be designed with the right incentives to
promote their deployment. Effective protection also requires
coordination between competing network providers. For the time
being, it is often difficult to even find the contact information for
operators of other networks.
A number of workshop participants shared the view that, if all the
known engineering approaches and bug fixes were universally deployed,
the Internet could have been enjoying a substantially reduced number
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of security problems today. In particular, the need for, and lack
of, BCP 38 deployment was mentioned numerous times during the
workshop. There is also a lack of enthusiasm about the routing
security requirements document being developed by the IETF RPSEC
(Routing Protocol Security) Working Group, which focuses heavily on
cryptographically-based protection requirements. Not only would
cryptographically-based solutions face the obstacle of funding for
deployment, but also they are likely to bring with them their own set
of problems.
4.3.3. Inadequate Education
There exists an educational challenge to disseminate the knowledge
needed for secure Internet usage and operations. Easily guessed
passwords and plaintext password transmission are still common in
many parts of the Internet. One common rumor claims that Cisco
routers were shipped with a default password "cisco" and this was
used by attackers to break into routers. In reality, operators often
configure Cisco routers with that password, perhaps because of the
difficulty of disseminating passwords to multiple maintainers. A
similar problem exists for Juniper routers and other vendors'
products.
How to provide effective education to the Internet user community at
large remains a great challenge. As mentioned earlier in this
report, the existence of a large number of compromised hosts is one
major source of the unwanted traffic problem, and the ultimate
solution to this problem is a well-informed, vigilant user community.
4.3.4. Is Closing Down Open Internet Access Necessary?
One position made at the workshop is that, facing the problems of
millions of vulnerable computers and lack of effective deterrence,
protecting the Internet might require a fundamental change to the
current Internet architecture, by replacing unconstrained open access
to the Internet with strictly controlled access. Although the
participants held different positions on this issue, a rough
consensus was reached that, considering the overall picture,
enforcing controlled access does not seem the best solution to
Internet protection. Instead, the workshop identified a number of
needs that should be satisfied to move towards a well protected
Internet:
o the need for risk assessment for service providers; at this time,
we lack a commonly agreed bar for security assurance;
o the need to add traceability to allow tracking of abnormal
behavior in the network, and
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o the need for liability if someone fails to follow recommended
practices.
Adding traceability has been difficult due to the distributed nature
of the Internet. Collaboration among operators is a necessity in
fighting cybercrimes. We must also pay attention to preparation for
the next cycle of miscreant activity, and not devote all our efforts
to fixing the existing problems. As discussed above, the current
reactive approach to security problems is not a winning strategy.
5. Active and Potential Solutions in the Pipeline
This section addresses the issues that vendors recognized as
important and for which there will be solutions available in the near
future.
There are a number of potential solutions that vendors are working
on, but are not yet offering as part of their product portfolio, that
will allegedly remedy or diagnose the problems described in
Section 4.1.
Inevitably, when vendors have or are about to make a decision on
implementing new features in their products but have not made any
announcement, the vendors are not willing to talk about the new
features openly, which limits what can be said in this section.
5.1. Central Policy Repository
One idea is to build a Central Policy Repository that holds policies
that are known to work properly, e.g., policies controlling from whom
one would accept traffic when under attack. This repository could,
for example, keep information on which neighbor router or AS is doing
proper ingress address filtering. The repository could also hold the
configurations that operators use to upgrade configurations on their
routers.
If such a repository is to be a shared resource used by multiple
operators, it will necessarily require validation and authentication
of the stored policies to ensure that the repository does not become
the cause of vulnerabilities. Inevitably, this would mean that the
information comes with a cost and it will only be viable if the sum
of the reductions in individual operators' costs is greater than the
costs of maintaining the repository.
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5.2. Flow Based Tools
A set of tools based on flow data is widely used to extract
information from both network and data link layers. Tools have been
built that can be used to find out the sources of almost any type of
traffic, including certain unwanted traffic. These flow-based tools
make it possible to do things like DDoS traceback, traffic/peering
analyses, and detection of botnets, worms, and spyware.
These tools monitor flows on the network and build baselines for what
is the "normal" behavior. Once the baseline is available, it is
possible to detect anomalous activity. It is easy to detect
variations over time, and decide if the variation is legitimate or
not. It is possible to take this approach further, typically
involving the identification of signatures of particular types of
traffic.
These flow-based tools are analogous to the "sonar" that is used by
navies to listen for submarines. Once a particular submarine is
identified, it is possible to record its sonar signature to be used
to provide rapid identification in the future when the same submarine
is encountered again.
Examples of existing tools include
Cisco IOS NetFlow <http://www.cisco.com/en/US/products/ps6601/
products_ios_protocol_group_home.html>,
sFlow <http://www.sflow.org/>, and
NeTraMet <http://www.caida.org/tools/measurement/netramet/> based on
the IETF RTFM and IPFIX standards.
There are also tools for working with the output of NetFlow such as
jFlow <http://www.net-track.ch/opensource/jflow/> and
Arbor Networks' Peakflow
<http://www.arbor.net/products_platform.php>.
The Cooperative Association for Internet Data Analysis (CAIDA)
maintains a taxonomy of available tools on its web site at
<http://www.caida.org/tools/taxonomy/index.xml>.
5.3. Internet Motion Sensor (IMS)
The Internet Motion Sensor (IMS) [IMS] may be used to watch traffic
to or from "Darknets" (routable prefixes that don't have end hosts
attached), unassigned address spaces, and unannounced address spaces.
By watching activities in these types of address spaces, one can
understand and detect, e.g., scanning activities, DDoS worms, worm
infected hosts, and misconfigured hosts.
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Currently, the IMS is used to monitor approximately 17 million
prefixes, about 1.2% of the IPv4 address space. The use of IMS has
highlighted two major characteristics of attacks; malicious attacks
are more targeted than one might have assumed, and a vulnerability in
a system does not necessarily lead to a threat to that system (e.g.,
the vulnerability may not be exploited to launch attacks if the
perceived "benefit" to the attacker appears small). Data from IMS
and other sources indicates that attackers are making increased use
of information from social networking sites to target their attacks
and select perceived easy targets, such as computers running very old
versions of systems or new, unpatched vulnerabilities.
This form of passive data collection is also known as a "Network
Telescope". Links to similar tools can be found on the CAIDA web
site at <http://www.caida.org/data/passive/network_telescope.xml>.
5.4. BCP 38
In the year 2000, the IETF developed a set of recommendations to
limit DOS attacks and Address Spoofing published as BCP 38 [RFC2827],
"Network Ingress Filtering: Defeating Denial of Service Attacks which
employ IP Source Address Spoofing". However, up to now BCP 38
capabilities still have not been widely deployed, perhaps due to the
incentive issue discussed earlier.
The IETF has also developed an additional set of recommendations
extending BCP 38 to multihomed networks. These recommendations are
published as BCP 84 [RFC3704].
5.5. Layer 5 to 7 Awareness
Tools are being developed that will make it possible to perform deep
packet inspection at high speed. Some companies are working on
hardware implementation to inspect all layers from 2 to 7 (e.g.,
EZchip <http://www.ezchip.com/t_npu_whpaper.htm>). A number of other
companies, including Cisco and Juniper, offer tools capable of
analyzing packets at the transport layer and above.
5.6. How To's
One idea that was discussed at the workshop envisaged operators and
standards bodies cooperating to produce a set of "How To" documents
as guidelines on how to configure networks. Dissemination and use of
these "How To's" should be encouraged by vendors, operators, and
standards bodies.
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This type of initiative needs a "sponsor" or "champion" that takes
the lead and starts collecting a set of "How To's" that could be
freely distributed. The workshop did not discuss this further.
5.7. SHRED
Methods to discourage the dissemination of spam by punishing the
spammers, such as Spam Harassment Reduction via Economic Disincentive
(SHRED) [SHRED], were discussed. The idea is to make it increasingly
expensive for spammers to use the email system, while normal users
retain what they have come to expect as normal service. There was no
agreement on the effectiveness of this type of system.
6. Research in Progress
In preparation for this session, several researchers active in
Internet Research were asked two rather open ended questions: "Where
is the focus on Internet research today?" and "Where should it be?"
A summary of the answers to these questions is given below.
Section 6.2.2 covers part of the relationship between research and
miscreants. For example, research activities in each area (please
refer to the slide set for Workshop Session 8 which can be found at
the link referred to in Appendix C).
6.1. Ongoing Research
Section 6.1 discusses briefly areas where we see active research on
unwanted traffic today.
6.1.1. Exploited Hosts
One area where researchers are very active is analyzing situations
where hosts are exploited. This has been a major focus for a long
time, and an abundance of reports have been published. Current
research may be divided into three different categories: prevention,
detection, and defense.
6.1.1.1. Prevention
Code quality is crucial when it comes to preventing exploitation of
Internet hosts. Quite a bit of research effort has therefore gone
into improvement of code quality. Researchers are looking into
automated methods for finding bugs and maybe in the end fixes for any
bugs detected.
A second approach designed to stop hosts from becoming compromised is
to reduce the "attack surface". Researchers are thinking about
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changes or extensions to the Internet architecture. The idea is to
create a strict client server architecture, where the clients only
are allowed to initiate connections, and while servers may only
accept connections.
Researchers have put a lot of effort into better scaling of honey
pots and honey farms to better understand and neutralize the methods
miscreants are using to exploit hosts. Research also goes into
developing honey monkeys in order to understand how hosts are
vulnerable. Both honey pots/farms and honey monkeys are aimed at
taking measures that prevent further (mis-)use of possible exploits.
6.1.1.2. Detection
When an attack is launched against a computer system, the attack
typically leaves evidence of the intrusion in the system logs. Each
type of intrusion leaves a specific kind of footprint or signature.
The signature can be evidence that certain software has been
executed, that logins have failed, that administrative privileges
have been misused, or that particular files and directories have been
accessed. Administrators can document these attack signatures and
use them to detect the same type of attack in the future. This
process can be automated.
Because each signature is different, it is possible for system
administrators to determine by looking at the intrusion signature
what the intrusion was, how and when it was perpetrated, and even how
skilled the intruder is.
Once an attack signature is available, it can be used to create a
vulnerability filter, i.e., the stored attack signature is compared
to actual events in real time and an alarm is given when this pattern
is repeated.
A further step may be taken with automated vulnerability signatures,
i.e., when a new type of attack is found, a vulnerability filter is
automatically created. This vulnerability filter can be made
available for nodes to defend themselves against this new type of
attack. The automated vulnerability signatures may be part of an
Intrusion Detection System (IDS).
6.1.1.3. Defense
An IDS can be a part of the defense against actual attacks, e.g., by
using vulnerability filters. An Intrusion Detection System (IDS)
inspects inbound and outbound network activities and detects
signatures that indicate that a system is under attack from someone
attempting to break into or compromise the system.
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6.1.2. Distributed Denial of Service (DDoS) Attacks
Research on DDoS attacks follows two separate approaches, the first
has the application as its focus, while the second focuses on the
network.
6.1.2.1. Application Oriented DDoS Research
The key issue with application oriented research is to distinguish
between legitimate activities and attacks. Today, several tools
exist that can do this and research has moved on to more advanced
things.
Research today looks into tools that can detect and filter activities
that have been generated by bots and botnets.
One approach is to set up a tool that sends challenges to senders
that want to send traffic to a certain node. The potential sender
then has to respond correctly to that challenge; otherwise, the
traffic will be filtered out.
The alternative is to get more capacity between sender and receiver.
This is done primarily by some form of use of peer-to-peer
technology.
Today, there is "peer-to-peer hype" in the research community; a sure
way of making yourself known as a researcher is to publish something
that solves old problems by means of some peer-to-peer technology.
Proposals now exist for peer-to-peer DNS, peer-to-peer backup
solutions, peer-to-peer web-cast, etc. Whether these proposals can
live up to the hype remains to be seen.
6.1.2.2. Network Oriented DDoS Research
Research on DDoS attacks that takes a network oriented focus may be
described by the following oversimplified three steps.
1. Find the bad stuff
2. Set the "evil bit" on those packets
3. Filter out the packets with the "evil bit" set
This rather uncomplicated scheme has to be carried out on high-speed
links and interfaces. Automation is the only way of achieving this.
One way of indirectly setting the "evil bit" is to use a normalized
TTL. The logic goes: the TTL for traffic from this sender has always
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been "x", but has now suddenly become "y", without any corresponding
change in routing. The conclusion is that someone is masquerading as
the legitimate sender. Traffic with the "y" TTL is filtered out.
Another idea is to give traffic received from ISPs that are known to
do source address validation the "red carpet treatment", i.e., to set
the "good bit". When an attack is detected, traffic from everyone
that doesn't have the "good bit" is filtered out. Apart from
reacting to the attack, this also give ISPs an incentive to do source
address validation. If they don't do it, their peers won't set the
"good bit" and the ISP's customers will suffer, dragging down their
reputation.
Overlay networks can also be used to stop a DDoS attack. The idea
here is that traffic is not routed directly to the destination.
Instead, it is hidden behind some entry points in the overlay. The
entry points make sure the sender is the host he claims he is, and in
that case, marks the packet with a "magic bit". Packets lacking the
"magic bit" are not forwarded on the overlay. This has good scaling
properties; you only need to have enough capacity to tag the amount
of traffic you want to receive, not the amount you actually receive.
6.1.3. Spyware
Current research on spyware and measurements of spyware are aiming to
find methods to understand when certain activities associated with
spyware happen and to understand the impact of this activity.
There are a number of research activities around spyware, e.g.,
looking into threats caused by spyware; however, these were only
briefly touched upon at the workshop.
6.1.4. Forensic Aids
Lately, research has started to look into tools and support to answer
the "What happened here?" question. These tools are called "forensic
aids", and can be used to "recreate" an illegal activity just as the
police do when working on a crime scene.
The techniques that these forensic aids take as their starting point
involve the identification of a process or program that should not be
present on a computer. The effort goes into building tools and
methods that can trace the intruder back to its origin. Methods to
understand how a specific output depends on a particular input also
exist.
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6.1.5. Measurements
Measurements are always interesting for the research community,
because they generate new data. Consequently, lots of effort goes
into specifying how measurements should be performed and into
development of measurement tools. Measurements have been useful in
creating effective counter-measures against worms. Before
measurements gave actual data of how worms behave, actions taken
against worms were generally ineffective.
6.1.6. Traffic Analysis
One aspect of research that closely relates to measurements is
analysis. Earlier, it was common to look for the amount of traffic
traversing certain transport ports. Lately, it has become common to
tunnel "everything" over something else, and a shift has occurred
towards looking for behavior and/or content. When you see a certain
behavior or content over a protocol that is not supposed to behave in
this way, it is likely that something bad is going on.
Since this is an arms race, the miscreants that use tunneling
protocols have started to mimic the pattern of something that is
acceptable.
6.1.7. Protocol and Software Security
The general IETF design guidelines for robust Internet protocols
says: "Be liberal in what you receive and conservative in what you
send". The downside is that most protocols believe what they get and
as a consequence also get what they deserve. The IAB is intending to
work on new design guidelines, e.g., rules of thumb and things you do
and things you don't. This is not ready yet, but will be offered as
input to a BCP in due course.
An area where there is a potential overlap between standards people
and researchers is protocol analysis languages. The protocol
analysis languages could be used, for example, look for
vulnerabilities.
6.2. Research on the Internet
The workshop discussed the interface between people working in
standardization organizations in general and IETF in particular on
the one hand and people working with research on the other. The
topic of discussion was broader than just "Unwanted traffic". Three
topics were touched on: what motivates researchers, how to attract
researchers to problems that are hindering or have been discovered in
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the context of standardization, and the sometimes rocky relations
between the research community and the "bad boys".
6.2.1. Research and Standards
The workshop discussed how research and standardization could
mutually support each other. Quite often there is a commonality of
interest between the two groups. The IAB supports the Internet
Research Task Force (IRTF) as a venue for Internet research. The
delta between what is done and what could be is still substantial.
The discussion focused on how standardization in general and the IETF
in particular can get help from researchers.
Since standardization organizations don't have the economic strength
to simply finance the research they need or want, other means have to
be used. One is to correctly and clearly communicate problems,
another is to supply adequate and relevant information.
To attract the research community to work with standardization
organizations, it is necessary to identify the real problems and
state them in such a way that they are amenable to solution. General
unspecified problems are of no use, e.g., "This is an impossible
problem!" or "All the problems are because my users behave badly!"
Instead, saying "This is an absolutely critical problem, and we have
no idea how to solve it!" is much more attractive.
The potential research problem should also be communicated in a way
that is public. A researcher that wants to take on a problem is
helped if she/he can point at a slide from NANOG or RIPE that
identifies this problem.
The way researchers go about solving problems is basically to
identify all the existing constraints, and then relax one of the
constraints and see what happens. Therefore, rock solid constraints
are a show stopper, e.g., "We can't do that, because it has to go
into an ASIC!". Real constraints have to be clearly communicated to
and understood by the researcher.
One reasonable way of fostering cooperation is to entice two or three
people and have them write a paper on the problem. What will happen
then is that this paper will be incrementally improved by other
researchers. The vast majority of all research goes into improving
on someone else's paper.
A second important factor is to supply sufficient relevant
information. New information that suggests possible ways to address
new problems or improve on old or partial solutions to previously
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investigated problems are attractive. Often, understanding of
important problems comes from the operator community; when trying to
initiate research from a standards perspective, keeping operators in
the loop may be beneficial.
Today, the research community is largely left on its own, and
consequently tends to generate essentially random, untargeted
results. If the right people in the standards community say the
right things to the right people in the research community, it can
literally focus hundreds of graduate students on a single problem.
Problem statements and data are needed.
6.2.2. Research and the Bad Guys
A general problem with all research and development is that what can
be used may also be misused. In some cases, miscreants have received
help from research that was never intended.
There are several examples of Free Nets, i.e., networks designed to
allow end-users to participate without revealing their identity or
how and where they are connected to the network. The Free Nets are
designed based on technologies such as onion routing or mix networks.
Free Nets create anonymity that allows people to express opinions
without having to reveal their true identity and thus can be used to
promote free speech. However, these are tools that can also work
just as well to hide illegal activities in democracies.
Mix networks create hard-to-trace communications by using a chain of
proxy servers. A message from a sender to a receiver passes by the
chain of proxies. A message is encrypted with a layered encryption
where each layer is understood by only one of the proxies in the
chain; the actual message is the innermost layer. A mix network will
achieve untraceable communication, even if all but one of the proxies
are compromised by a potential tracer.
Onion routing is a technique for anonymous communication over a
computer network; it is a technique that encodes routing information
in a set of encrypted layers. Onion routing is a further development
of mix networks.
Research projects have resulted in methods for distributed command
and control, e.g., in the form of Distributed Hash Tables (DHT) and
gossip protocols. This of course has legitimate uses, e.g., for
security and reliability applications, but it also is extremely
useful for DDoS attacks and unwanted traffic in general.
A lot of effort has gone into research around worms, the result is
that we have a very good understanding of the characteristics of the
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technology associated with worms and how they behave. This is a very
good basis when we want to protect against worms. The downside is
that researchers also understand how to implement future worms,
including knowledge on how to design faster worms that won't leave a
footprint.
7. Aladdin's Lamp
If we had an Aladdin's Lamp and could be granted anything we wanted
in the context of remedying unwanted traffic or effects of such
traffic - what would we wish for? The topic of this session was
wishes, i.e., loosening the constraints that depend on what we have
and focus on what we really want.
There certainly are lots of "wishes" around, not least of which is
making things simpler and safer. On the other hand, very few of
these wishes are clearly stated. One comment on this lack of clarity
was that we are too busy putting out the fires of today and don't
have the time to be thinking ahead.
7.1. Security Improvements
Operators at the workshop expressed a number of wishes that, if
fulfilled, would help to improve and simplify security. The list
below contains a number of examples of actions that ought to improve
security. The content is still at the "wish-level", i.e., no effort
has gone in to trying to understand the feasibility of realizing
these wishes.
Wish: Reliable point of contact in each administrative domain for
security coordination.
First and foremost, operators would like to see correct and complete
contact information to coordinate security problems across operators.
The "whois" database of registration details for IP addresses and
Autonomous System numbers held by Regional Internet Registries (e.g.,
ARIN, RIPE, APNIC) was intended to be a directory for this type of
information, and RFC 2142 [RFC2142] established common mailbox names
for certain roles and services. There are several reasons why these
tools are largely unused, including unwanted traffic.
Wish: Organized testing for security.
Today, new hardware and software are extensively tested for
performance. There is almost no testing of this hardware and
software for security.
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Wish: Infrastructure or test bed for security.
It would be good to have an organized infrastructure or test bed for
testing of security for new products.
Wish: Defaults for security.
Equipment and software should come with a simple and effective
default setting for security.
Wish: Shared information regarding attacks.
It would be useful to have an automated sharing mechanism for
attacks, vulnerabilities, and sources of threats between network
users and providers in order to meet attacks in a more timely and
efficient manner.
7.2. Unwanted Traffic
Wish: Automatic filtering of unwanted traffic.
It would be useful, not least for enterprises, to have mechanisms
that would automatically filter out the unwanted traffic.
Some filtering of spam, viruses, and malware that is sent by email is
already practicable but inevitably is imperfect because it mainly
relies on "heuristics" to identify the unwanted traffic. This is
another example of the "arms race" between filtering and the
ingenuity of spammers trying to evade the filters. This "wish" needs
to be further discussed and developed to make it something that could
be turned into practical ideas.
Wish: Fix Spam.
A large fraction of the email traffic coming into enterprises today
is spam, and consequently any fixes to the spam problem are very high
on their priority list.
8. Workshop Summary
The workshop spent its last two hours discussing the following
question: What are the engineering (immediate and longer term) and
research issues that might be pursued within the IETF and the IRTF,
and what actions could the IAB take? The suggested actions can be
summarized into three classes.
8.1. Hard Questions
The discussions during this concluding section raised a number of
questions that touched upon the overall network architecture designs.
o What should be the roles of cryptographic mechanisms in the
overall Internet architecture? For example, do we need to apply
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cryptographic mechanisms to harden the shell, or rely on deep
packet inspection to filter out bad traffic?
o To add effective protection to the Internet, how far are we
willing to go in
* curtailing its openness, and
* increasing the system complexity?
And what architectural principles do we need to preserve as we go
along these paths?
o A simple risk analysis would suggest that an ideal attack target
of minimal cost but maximal disruption is the core routing
infrastructure. However, do we really need an unlinked and
separately managed control plane to secure it? This requires a
deep understanding of the architectural design trade-offs.
o Can we, and how do we, change the economic substructure? A
special workshop was suggested as a next step to gain a better
understanding of the question.
8.2. Medium or Long Term Steps
While answering the above hard questions may take some time and
effort, several specific steps were suggested as medium or long term
efforts to add protection to the Internet:
o Tightening the security of the core routing infrastructure.
o Cleaning up the Internet Routing Registry repository [IRR], and
securing both the database and the access, so that it can be used
for routing verifications.
o Take down botnets.
o Although we do not have a magic wand to wave all the unwanted
traffic off the Internet, we should be able to develop effective
measures to reduce the unwanted traffic to a tiny fraction of its
current volume and keep it under control.
o Community education, to try to ensure people *use* updated host,
router, and ingress filtering BCPs.
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8.3. Immediately Actionable Steps
The IETF is recommended to take steps to carry out the following
actions towards enhancing the network protection.
o Update the host requirements RFC. The Internet host requirements
([RFC1122], [RFC1123]) were developed in 1989. The Internet has
gone through fundamental changes since then, including the
pervasive security threats. Thus, a new set of requirements is
overdue.
o Update the router requirements. The original router requirements
[RFC1812] were developed in 1995. As with the host requirements,
it is also overdue for an update.
o Update ingress filtering (BCP 38 [RFC2827] and BCP 84 [RFC3704]).
One immediate action that the IAB should carry out is to inform the
community about the existence of the underground economy.
The IRTF is recommended to take further steps toward understanding
the Underground Economy and to initiate research on developing
effective countermeasures.
Overall, the workshop attendees wish to raise the community's
awareness of the underground economy. The community as a whole
should undertake a systematic examination of the current situation
and develop both near- and long-term plans.
9. Terminology
This section gives an overview of some of the key concepts and
terminology used in this document. It is not intended to be
complete, but is offered as a quick reference for the reader of the
report.
ACL
Access Control List in the context of Internet networking refers to a
set of IP addresses or routing prefixes (layer 3 or Internet layer
information), possibly combined with transport protocol port numbers
(layer 4 or transport layer information). The layer 3 and/or layer 4
information in the packets making up a flow entering or leaving a
device in the Internet is matched against the entries in an ACL to
determine whether the packets should, for example, be allowed or
denied access to some resources. The ACL effectively specifies a
filter to be used on a flow of packets.
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BGP route hijacking
Attack in which an inappropriate route is injected into the global
routing system with the intent of diverting traffic from its intended
recipient either as a DoS attack (q.v.) where the traffic is just
dropped or as part of some wider attack on the recipient. Injecting
spurious routes specifying addresses used for bogons can, for
example, provide bogus assurance to email systems that spam is coming
from legitimate addresses.
Bogon
A bogon is an IP packet that has a source address taken for a range
of addresses that has not yet been allocated to legitimate users, or
is a private [RFC1918] or reserved address [RFC3330].
Bogon prefix
A bogon prefix is a route that should never appear in the Internet
routing table, e.g., from the private or unallocated address blocks.
Bot
A bot is common parlance on the Internet for a software program that
is a software agent. A Bot interacts with other network services
intended for people as if it were a real person. One typical use of
bots is to gather information. The term is derived from the word
"robot," reflecting the autonomous character in the "virtual robot"-
ness of the concept.
The most common bots are those that covertly install themselves on
people's computers for malicious purposes, and that have been
described as remote attack tools. Bots are sometimes called
"zombies".
Botnet
Botnet is a jargon term for a collection of software robots, or bots,
which run autonomously. This can also refer to the network of
computers using distributed computing software. While the term
"botnet" can be used to refer to any group of bots, such as IRC bots,
the word is generally used to refer to a collection of compromised
machines running programs, usually referred to as worms, Trojan
horses, or backdoors, under a common command and control
infrastructure.
Click fraud
Click fraud occurs in pay per click (PPC) advertising when a person,
automated script, or computer program imitates a legitimate user of a
web browser clicking on an ad for the purpose of generating an
improper charge per click. Pay per click advertising is when
operators of web sites act as publishers and offer clickable links
from advertisers in exchange for a charge per click.
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Darknet
A Darknet (also known as a Network Telescope, a Blackhole, or an
Internet Sink) is a globally routed network that has no "real"
machines attached and carries only a very small amount of specially
crafted legitimate traffic. It is therefore easily possible to
separate out and analyze unwanted traffic that can arise from a wide
variety of events including misconfiguration (e.g., a human being
mis-typing an IP address), malicious scanning of address space by
hackers looking for vulnerable targets, backscatter from random
source denial-of-service attacks, and the automated spread of
malicious software called Internet worms.
Dirty affiliate program
Affiliate programs are distributed marketing programs that recruit
agents to promote a product or service. Affiliates get financially
compensated for each sale associated with their unique 'affiliate
ID.' Affiliates are normally instructed by the operator of the
affiliate program to not break any laws while promoting the product
or service. Sanctions (typically loss of unpaid commissions or
removal from the affiliate program) are normally applied if the
affiliate spams or otherwise violates the affiliate program's
policies.
Dirty affiliate programs allow spamming, or if they do nominally
prohibit spamming, they don't actually sanction violators. Dirty
affiliate programs often promote illegal or deceptive products
(prescription drugs distributed without regard to normal dispensing
requirements, body part enlargement products, etc.), employ anonymous
or untraceable affiliates, offer payment via anonymous online
financial channels, and may fail to follow normal tax withholding and
reporting practices.
DoS attack
Denial-Of-Service attack, a type of attack on a network that is
designed to bring the network to its knees by flooding it with
useless traffic or otherwise blocking resources necessary to allow
normal traffic flow.
DDoS attack
Distributed Denial of Service, an attack where multiple compromised
systems are used to target a single system causing a Denial of
Service (DoS) attack.
Honey farm
A honey farm is a set of honey pots working together.
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Honey monkey
A honey monkey is a honey pot in reverse; instead of sitting and
waiting for miscreants, a honey monkey actively mimics the actions of
a user surfing the Web. The honey monkey runs on virtual machines in
order to detect exploit sites.
Honey pot
A honey pot is a server attached to the Internet that acts as a
decoy, attracting potential miscreants in order to study their
activities and monitor how they are able to break into a system.
Honeypots are designed to mimic systems that an intruder would like
to break into but limit the intruder from having access to an entire
network.
IRC
Internet Relay Chat is a form of instant communication over the
Internet. It is mainly designed for group (many-to-many)
communication in discussion forums called channels, but also allows
one-to-one communication, originally standardized by RFC 1459
[RFC1459] but much improved and extended since its original
invention. IRC clients rendezvous and exchange messages through IRC
servers. IRC servers are run by many organizations for both benign
and nefarious purposes.
Malware
Malware is software designed to infiltrate or damage a computer
system, without the owner's informed consent. There are
disagreements about the etymology of the term itself, the primary
uncertainty being whether it is a portmanteau word (of "malicious"
and "software") or simply composed of the prefix "mal-" and the
morpheme "ware". Malware references the intent of the creator,
rather than any particular features. It includes computer viruses,
worms, Trojan horses, spyware, adware, and other malicious and
unwanted software. In law, malware is sometimes known as a computer
contaminant.
Mix networks
Mix networks create hard-to-trace communications by using a chain of
proxy servers [MIX]. Each message is encrypted to each proxy; the
resulting encryption is layered like a Russian doll with the message
as the innermost layer. Even if all but one of the proxies are
compromised by a tracer, untraceability is still achieved. More
information can be found at
<http://www.adastral.ucl.ac.uk/~helger/crypto/link/protocols/
mix.php>.
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Onion routing
Onion routing is a technique for anonymous communication over a
computer network, it is a technique that encodes routing information
in a set of encrypted layers. Onion routing is based on mix cascades
(see mix networks (q.v.)). More information can be found at
<http://www.onion-router.net/>.
Phishing
Phishing is a form of criminal activity using social engineering
techniques. It is characterized by attempts to fraudulently acquire
sensitive information, such as passwords and credit card details, by
masquerading as a trustworthy person or business in an apparently
official electronic communication. Phishing is typically carried out
using spoofed websites, email, or an instant message. The term
phishing derives from password harvesting and the use of increasingly
sophisticated lures to "fish" for users' financial information and
passwords.
Root access
Access to a system with full administrative privileges bypassing any
security restrictions placed on normal users. Derived from the name
traditionally used for the 'superuser' on Unix systems.
Script kiddy
Derogatory term for an inexperienced hacker who mindlessly uses
scripts and other programs developed by others with the intent of
compromising computers or generating DoS attacks.
Spam
Spamming is the abuse of electronic messaging systems to send
unsolicited, undesired bulk messages. The individual messages are
refereed to as spam. The term is frequently used to refer
specifically to the electronic mail form of spam.
Spoofing
(IP) spoofing is a technique where the illegitimate source of IP
packets is obfuscated by contriving to use IP address(es) that the
receiver recognizes as a legitimate source. Spoofing is often used
to gain unauthorized access to computers or mislead filtering
mechanisms, whereby the intruder sends packets into the network with
an IP source address indicating that the message is coming from a
legitimate host. To engage in IP spoofing, a hacker must first use a
variety of techniques to find an IP address of a valid host and then
modify the packet headers so that it appears that the packets are
coming from that host.
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Spyware
Any software that covertly gathers user information through the
user's Internet connection without his or her knowledge, e.g., for
spam purposes.
UBE
Unsolicited Bulk Email: an official term for spam.
UCE
Unsolicited Commercial Email: an official term for spam.
Virus
A program or piece of code that is loaded onto a computer without the
owner's knowledge and runs without their consent. A virus is self-
replicating code that spreads by inserting copies of itself into
other executable code or documents, which are then transferred to
other machines. Typically, the virus has a payload that causes some
harm to the infected machine when the virus code is executed.
Worm
A computer worm is a self-replicating computer program. It uses a
network to send copies of itself to other systems and it may do so
without any user intervention. Unlike a virus, it does not need to
attach itself to an existing program. Worms always harm the network
(if only by consuming bandwidth), whereas viruses always infect or
corrupt files on a targeted computer.
Zombie
This is another name for a bot.
10. Security Considerations
This document does not specify any protocol or "bits on the wire".
11. Acknowledgements
The IAB would like to thank the University of Southern California
Information Sciences Institute (ISI) who hosted the workshop and all
those people at ISI and elsewhere who assisted with the organization
and logistics of the workshop at ISI.
The IAB would also like to thank the scribes listed in Appendix A who
diligently recorded the proceedings during the workshop.
A special thanks to all the participants in the workshop, who took
the time, came to the workshop to participate in the discussions, and
who put in the effort to make this workshop a success. The IAB
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especially appreciates the effort of those that prepared and made
presentations at the workshop.
12. Informative References
[IMS] University of Michigan, "Internet Motion Sensor", 2006,
<http://ims.eecs.umich.edu/>.
[IRR] Merit Network Inc, "Internet Routing Registry Routing
Assets Database", 2006, <http://www.irr.net/>.
[MIX] Hill, R., Hwang, A., and D. Molnar, "Approaches to Mix
Nets", MIT 6.857 Final Project, December 1999, <http://
www.mit.edu/afs/athena/course/6/6.857/OldStuff/Fall99/
papers/mixnet.ps.gz>.
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[RFC1459] Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol",
RFC 1459, May 1993.
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers",
RFC 1812, June 1995.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND
FUNCTIONS", RFC 2142, May 1997.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330,
September 2002.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, March 2004.
[SHRED] Krishnamurthy, B. and E. Blackmond, "SHRED: Spam
Harassment Reduction via Economic Disincentives", 2003,
<http://www.research.att.com/~bala/papers/shred-ext.ps>.
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Appendix A. Participants in the Workshop
Bernard Aboba (IAB)
Loa Andersson (IAB)
Ganesha Bhaskara (scribe)
Bryan Burns
Leslie Daigle (IAB chair)
Sean Donelan
Rich Draves (IAB Executive Director)
Aaron Falk (IAB, IRTF chair)
Robert Geigle
Minas Gjoka (scribe)
Barry Greene
Sam Hartman (IESG, Security Area Director)
Bob Hinden (IAB)
Russ Housely (IESG, Security Area Director)
Craig Huegen
Cullen Jennings
Rodney Joffe
Mark Kosters
Bala Krishnamurthy
Gregory Lebovitz
Ryan McDowell
Danny McPherson
Dave Merrill
David Meyer (IAB)
Alan Mitchell
John Morris
Eric Osterweil (scribe)
Eric Rescorla (IAB)
Pete Resnick (IAB)
Stefan Savage
Joe St Sauver
Michael Sirivianos (scribe)
Rob Thomas
Helen Wang
Lixia Zhang (IAB)
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Appendix B. Workshop Agenda
Session 1:
How bad is the problem? What are the most important symptoms?
Session 2:
What are the sources of the problem?
Lunch session (session 3):
Solutions in regulatory and societal space
Session 4:
The underground economy
Session 5:
Current countermeasures, what works, what doesn't
Session 6:
If all our wishes could be granted, what would they be?
Session 7:
What's in the pipeline, or should be in the pipeline
Session 8:
What is being actively researched on?
Session 9:
What are the engineering (immediate and longer term) and
research issues that might be pursued within the IETF/IAB/IRTF?
Appendix C. Slides
Links to a subset of the presentations given by the participants at
the workshop can be found via the IAB Workshops page on the IAB web
site at <http://utgard.ietf.org/iab/about/workshops/unwantedtraffic/
index.html>. As mentioned in Section 1, this is not a complete set
of the presentations because certain of the presentations were of a
sensitive nature which it would be inappropriate to make public at
this time.
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Authors' Addresses
Loa Andersson
Acreo AB
EMail: loa@pi.se
Elwyn Davies
Folly Consulting
EMail: elwynd@dial.pipex.com
Lixia Zhang
UCLA
EMail: lixia@cs.ucla.edu
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Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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Funding for the RFC Editor function is currently provided by the
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ERRATA
