This is a purely informative rendering of an RFC that includes verified errata. This rendering may not be used as a reference.

The following 'Verified' errata have been incorporated in this document: EID 1024
Network Working Group                                       L. Andersson
Request for Comments: 4948                                      Acreo AB
Category: Informational                                        E. Davies
                                                        Folly Consulting
                                                                L. Zhang
                                                             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).


   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.

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

   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

   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.

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

   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.

   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.

   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

   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.

   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

   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.

   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

   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

   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.

   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

      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

   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

   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

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

   Working Group; however, many DNS operators have not taken appropriate

   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

   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

      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

   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

   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

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.

   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 package was discovered and fixed in 2003, yet a number of DNS 
EID 1024 (Verified) is as follows:

Section: 4.3.2

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for example, a bug in the BIND packet was discovered

Corrected Text:

for example, a bug in the BIND package was discovered
from pending
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 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 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. 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 < products_ios_protocol_group_home.html>, sFlow <>, and NeTraMet <> based on the IETF RTFM and IPFIX standards. There are also tools for working with the output of NetFlow such as jFlow <> and Arbor Networks' Peakflow <>. The Cooperative Association for Internet Data Analysis (CAIDA) maintains a taxonomy of available tools on its web site at <>. 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. 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 <>. 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 <>). 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. 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. 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 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. 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). 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. 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. 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. 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 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. 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 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 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 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. 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 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. 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. 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. 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. 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 < mix.php>. 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 <>. 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. 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 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, <>. [IRR] Merit Network Inc, "Internet Routing Registry Routing Assets Database", 2006, <>. [MIX] Hill, R., Hwang, A., and D. Molnar, "Approaches to Mix Nets", MIT 6.857 Final Project, December 1999, <http:// papers/>. [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, <>. 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) 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 < 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. Authors' Addresses Loa Andersson Acreo AB EMail: Elwyn Davies Folly Consulting EMail: Lixia Zhang UCLA EMail: 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 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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