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Network Working Group                                       L. AnderssonRequest for Comments: 4948                                      Acreo ABCategory: Informational                                        E. Davies                                                        Folly Consulting                                                                L. Zhang                                                                    UCLA                                                             August 2007Report from the IAB workshop on Unwanted Traffic March 9-10, 2006Status of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The IETF Trust (2007).Abstract   This document reports the outcome of a workshop held by the Internet   Architecture Board (IAB) on Unwanted Internet Traffic.  The workshop   was held on March 9-10, 2006 at USC/ISI in Marina del Rey, CA, USA.   The primary goal of the workshop was to foster interchange between   the operator, standards, and research communities on the topic of   unwanted traffic, as manifested in, for example, Distributed Denial   of Service (DDoS) attacks, spam, and phishing, to gain understandings   on the ultimate sources of these unwanted traffic, and to assess   their impact and the effectiveness of existing solutions.  It was   also a goal of the workshop to identify engineering and research   topics that could be undertaken by the IAB, the IETF, the IRTF, and   the network research and development community at large to develop   effective countermeasures against the unwanted traffic.Andersson, et al.            Informational                      [Page 1]

RFC 4948                    Unwanted Traffic                 August 2007Table of Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .32.  The Root of All Evils: An Underground Economy  . . . . . . . .42.1.  The Underground Economy  . . . . . . . . . . . . . . . . .52.2.  Our Enemy Using Our Networks, Our Tools  . . . . . . . . .62.3.  Compromised Systems Being a Major Source of Problems . . .72.4.  Lack of Meaningful Deterrence  . . . . . . . . . . . . . .82.5.  Consequences . . . . . . . . . . . . . . . . . . . . . . .103.  How Bad Is The Problem?  . . . . . . . . . . . . . . . . . . .103.1.  Backbone Providers . . . . . . . . . . . . . . . . . . . .103.1.1.  DDoS Traffic . . . . . . . . . . . . . . . . . . . . .103.1.2.  Problem Mitigation . . . . . . . . . . . . . . . . . .113.2.  Access Providers . . . . . . . . . . . . . . . . . . . . .12     3.3.  Enterprise Networks: Perspective from a Large           Enterprise . . . . . . . . . . . . . . . . . . . . . . . .133.4.  Domain Name Services . . . . . . . . . . . . . . . . . . .144.  Current Vulnerabilities and Existing Solutions . . . . . . . .154.1.  Internet Vulnerabilities . . . . . . . . . . . . . . . . .154.2.  Existing Solutions . . . . . . . . . . . . . . . . . . . .164.2.1.  Existing Solutions for Backbone Providers  . . . . . .164.2.2.  Existing Solutions for Enterprise Networks . . . . . .174.3.  Shortfalls in the Existing Network Protection  . . . . . .184.3.1.  Inadequate Tools . . . . . . . . . . . . . . . . . . .184.3.2.  Inadequate Deployments . . . . . . . . . . . . . . . .184.3.3.  Inadequate Education . . . . . . . . . . . . . . . . .194.3.4.  Is Closing Down Open Internet Access Necessary?  . . .195.  Active and Potential Solutions in the Pipeline . . . . . . . .205.1.  Central Policy Repository  . . . . . . . . . . . . . . . .205.2.  Flow Based Tools . . . . . . . . . . . . . . . . . . . . .215.3.  Internet Motion Sensor (IMS) . . . . . . . . . . . . . . .215.4.BCP 38 . . . . . . . . . . . . . . . . . . . . . . . . . .225.5.  Layer 5 to 7 Awareness . . . . . . . . . . . . . . . . . .225.6.  How To's . . . . . . . . . . . . . . . . . . . . . . . . .225.7.  SHRED  . . . . . . . . . . . . . . . . . . . . . . . . . .236.  Research in Progress . . . . . . . . . . . . . . . . . . . . .236.1.  Ongoing Research . . . . . . . . . . . . . . . . . . . . .236.1.1.  Exploited Hosts  . . . . . . . . . . . . . . . . . . .236.1.2.  Distributed Denial of Service (DDoS) Attacks . . . . .256.1.3.  Spyware  . . . . . . . . . . . . . . . . . . . . . . .266.1.4.  Forensic Aids  . . . . . . . . . . . . . . . . . . . .266.1.5.  Measurements . . . . . . . . . . . . . . . . . . . . .276.1.6.  Traffic Analysis . . . . . . . . . . . . . . . . . . .276.1.7.  Protocol and Software Security . . . . . . . . . . . .276.2.  Research on the Internet . . . . . . . . . . . . . . . . .276.2.1.  Research and Standards . . . . . . . . . . . . . . . .286.2.2.  Research and the Bad Guys  . . . . . . . . . . . . . .29Andersson, et al.            Informational                      [Page 2]

RFC 4948                    Unwanted Traffic                 August 20077.  Aladdin's Lamp . . . . . . . . . . . . . . . . . . . . . . . .307.1.  Security Improvements  . . . . . . . . . . . . . . . . . .307.2.  Unwanted Traffic . . . . . . . . . . . . . . . . . . . . .318.  Workshop Summary . . . . . . . . . . . . . . . . . . . . . . .318.1.  Hard Questions . . . . . . . . . . . . . . . . . . . . . .318.2.  Medium or Long Term Steps  . . . . . . . . . . . . . . . .328.3.  Immediately Actionable Steps . . . . . . . . . . . . . . .339.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .3310. Security Considerations  . . . . . . . . . . . . . . . . . . .3811. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .3812. Informative References . . . . . . . . . . . . . . . . . . . .39Appendix A.  Participants in the Workshop  . . . . . . . . . . . .40Appendix B.  Workshop Agenda . . . . . . . . . . . . . . . . . . .41Appendix C.  Slides  . . . . . . . . . . . . . . . . . . . . . . .411.  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 theAndersson, et al.            Informational                      [Page 3]

RFC 4948                    Unwanted Traffic                 August 2007   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 inAppendix A.  The agenda   of the workshop can be found inAppendix B.  Links to a subset of the   presentations are provided inAppendix 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 inSection 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.Andersson, et al.            Informational                      [Page 4]

RFC 4948                    Unwanted Traffic                 August 20072.1.  The Underground Economy   As in any economic system, the underground economy is regulated by a   demand and supply chain.  The underground economy, which began as a   barter system, has evolved into a giant shopping mall, commonly   running on IRC (Internet Relay Chat) servers.  The IRC servers   provide various online stores selling information about stolen credit   cards and bank accounts, malware, bot code, botnets, root accesses to   compromised hosts and web servers, and much more.  There are DDoS   attack stores, credit card stores, PayPal and bank account stores, as   well as Cisco and Juniper router stores that sell access to   compromised routers.  Although not everything can be found on every   server, most common tools used to operate in the underground economy   can be found on almost all the servers.   How do miscreants turn attack tools and compromised machines into   real assets?  In the simplest case, miscreants electronically   transfer money from stolen bank accounts directly to an account that   they control, often in another country.  In a more sophisticated   example, miscreants use stolen credit cards or PayPal accounts for   online purchases.  To hide their trails, they often find remailers   who receive the purchased goods and then repackage them to send to   the miscreants for a fee.  The miscreants may also sell the goods   through online merchandising sites such as eBay.  They request the   payments be made in cashier checks or money orders to be sent to the   people who provide money laundering services for the miscreants by   receiving the payments and sending them to banks in a different   country, again in exchange for a fee.  In either case, the   destination bank accounts are used only for a short period and are   closed as soon as the money is withdrawn by the miscreants.   The miscreants obtain private and financial information from   compromised hosts and install bots (a.k.a. zombies) on them.  They   can also obtain such information from phishing attacks.  Spam   messages mislead naive users into accessing spoofed web sites run by   the miscreants where their financial information is extracted and   collected.   The miscreants in general are not skilled programmers.  With money,   however, they can hire professional writers to produce well phrased   spam messages, and hire coders to develop new viruses, worms,   spyware, and botnet control packages, thereby resupplying the   underground market with new tools that produce more unwanted traffic   on the Internet: spam messages that spread phishing attacks, botnets   that are used to launch DDoS attacks, click fraud that "earns" income   by deceiving online commercial advertisers, and new viruses and worms   that compromise more hosts and steal additional financial information   as well as system passwords and personal identity information.Andersson, et al.            Informational                      [Page 5]

RFC 4948                    Unwanted Traffic                 August 2007   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.Andersson, et al.            Informational                      [Page 6]

RFC 4948                    Unwanted Traffic                 August 2007   Our enemies make good use of the Internet's global connectivity as   well as all the tools the Internet has developed.  IRC servers   provide a job market for the miscreants and shopping malls of attack   tools.  Networking research has produced abundant results making it   easier to build large scale distributed systems, and these have been   adopted by miscreants to build large size, well-controlled botnets.   Powerful search engines also enable one to quickly find readily   available tools and resources.  The sophistication of attacks has   increased with time, while the skills required to launch effective   attacks have become minimal.  Attackers can be hiding anywhere in the   Internet while attacks get launched on a global scale.2.3.  Compromised Systems Being a Major Source of Problems   The current Internet provides a field ripe for exploitation.  The   majority of end hosts run vulnerable platforms.  People from all   walks of life eagerly jump into the newly discovered online world,   yet without the proper training needed to understand the full   implications.  This is at least partially due to most users failing   to anticipate how such a great invention can be readily abused.  As a   result, the Internet has ended up with a huge number of compromised   hosts, without their owners being aware that it has happened.   Unprotected hosts can be compromised in multiple ways.  Viruses and   worms can get into the system through exploiting bugs in the existing   operating systems or applications, sometimes even in anti-virus   programs.  A phishing site may also take the opportunity to install   malware on a victim's computer when a user is lured to the site.   More recently, viruses have also started being propagated through   popular peer-to-peer file sharing applications.  With multiple   channels of propagation, malware has become wide-spread, and infected   machines include not only home PCs (although they do represent a   large percentage), but also corporate servers, and even government   firewalls.   News of new exploits of vulnerabilities of Microsoft Windows   platforms is all too frequent, which leads to a common perception   that the Microsoft Windows platform is a major source of   vulnerability.  One of the reasons for the frequent vulnerability   exploits of the Windows system is its popularity in the market place;   thus, a miscreant's investment in each exploit can gain big returns   from infecting millions of machines.  As a result, each incident is   also likely to make headlines in the news.  In reality, all other   platforms such as Linux, Solaris, and MAC OS for example, are also   vulnerable to compromises.  Routers are not exempt from security   break-ins either, and using a high-end router as a DoS launchpad can   be a lot more effective than using a bundle of home PCs.Andersson, et al.            Informational                      [Page 7]

RFC 4948                    Unwanted Traffic                 August 2007   Quietly subverting large numbers of hosts and making them part of a   botnet, while leaving their normal functionality and connectivity   essentially unimpaired, is now a major aim of miscreants and it   appears that they are being all too successful.  Bots and the   functions they perform are often hard to detect and most of the time   their existence are not known to system operators or owners (hence,   the alternative name for hosts infected with bots controlled by   miscreants - zombies); by the time they are detected, it might very   well be too late as they have carried out the intended   (mal-)function.   The existence of a large number of compromised hosts is a   particularly challenging problem to the Internet's security.  Not   only does the stolen financial information lead to enormous economic   losses, but also there has been no quick fix to the problem.  As   noted above, in many cases the owners of the compromised computers   are unaware of the problem.  Even after being notified, some owners   still do not care about fixing the problem as long as their own   interest, such as playing online games, is not affected, even though   the public interest is endangered --- large botnets can use multi-   millions of such compromised hosts to launch DDoS attacks, with each   host sending an insignificant amount of traffic but the aggregate   exceeding the capacity of the best engineered systems.2.4.  Lack of Meaningful Deterrence   One of the Internet's big strengths is its ability to provide   seamless interconnection among an effectively unlimited number of   parties.  However, the other side of the same coin is that there may   not be clear ways to assign responsibilities when something goes   wrong.  Taking DDoS attacks as an example, an attack is normally   launched from a large number of compromised hosts, the attack traffic   travels across the Internet backbone to the access network(s) linking   to the victims.  As one can see, there are a number of independent   stake-holders involved, and it is not immediately clear which party   should take responsibility for resolving the problem.   Furthermore, tracking down an attack is an extremely difficult task.   The Internet architecture enables any IP host to communicate with any   other hosts, and it provides no audit trails.  As a result, not only   is there no limit to what a host may do, but also there is no trace   after the event of what a host may have done.  At this time, there is   virtually no effective tool available for problem diagnosis or packet   trace back.  Thus, tracking down an attack is labor intensive and   requires sophisticated skills.  As will be mentioned in the next   section, there is also a lack of incentive to report security   attacks.  Compounded with the high cost, these factors make forensic   tracing of an attack to its root a rare event.Andersson, et al.            Informational                      [Page 8]

RFC 4948                    Unwanted Traffic                 August 2007   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 byAndersson, et al.            Informational                      [Page 9]

RFC 4948                    Unwanted Traffic                 August 2007   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 butAndersson, et al.            Informational                     [Page 10]

RFC 4948                    Unwanted Traffic                 August 2007   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.Andersson, et al.            Informational                     [Page 11]

RFC 4948                    Unwanted Traffic                 August 2007   However, these tools are rather rudimentary and inadequate, as we   will elaborate inSection 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 isAndersson, et al.            Informational                     [Page 12]

RFC 4948                    Unwanted Traffic                 August 2007      released, and approximately 40% of the remaining vulnerable      computers in each following month will show signs of being      patched.  This leaves a few percent still unpatched after 6      months.  In the very large population of Internet hosts, this      results in a significant number of hosts that will be vulnerable      for the rest of their life.   o  There is a general lack of user understanding: after being      compromised, unmanaged computers may get replaced rather than      repaired, and this often results in infections occurring during      the installation process on the replacement.3.3.  Enterprise Networks: Perspective from a Large Enterprise   The operators of one big enterprise network reported their experience   regarding unwanted traffic to the workshop.  Enterprises perceive   many forms of bad traffic including worms, malware, spam, spyware,   Instant Messaging (IM), peer-to-peer (P2P) traffic, and DoS.   Compared to backbone and access providers, enterprise network   operators are more willing to investigate security breaches, although   they may hesitate to pay a high price for security solutions.  False   positives are very costly.  Most operators prefer false negatives to   false positives.  In general, enterprises prefer prevention solutions   to detection solutions.   Deliberately created unwanted traffic (as opposed to unwanted traffic   that might arise from misconfiguration) in enterprise networks can be   sorted into three categories.  The first is "Nuisance", which   includes unwanted traffic such as spam and peer-to-peer file sharing.   Although there were different opinions among the workshop   participants as to whether P2P traffic should, or should not, be   considered as unwanted traffic, enterprise network operators are   concerned not only that P2P traffic represents a significant share of   the total network load, but they are also sensitive to potential   copyright infringement issues that might lead to significant   financial and legal impacts on the company as a whole.  In addition,   P2P file sharing applications have also became a popular channel for   malware propagation.   The second category of unwanted traffic is labeled "Malicious", which   includes the traffic that spreads malware.  This class of traffic can   be small in volume but the cost from the resulting damage can be   high.  The clean up after an incident also requires highly skilled   operators.   The third category of unwanted traffic is "Unknown": it is known that   there exists a class of traffic in the network that can be best   described in this way, as no one knows its purpose or the locationsAndersson, et al.            Informational                     [Page 13]

RFC 4948                    Unwanted Traffic                 August 2007   of the sources.  Malicious traffic can be obscured by encryption,   encapsulation, or covered up as legitimate traffic.  The existing   detection tools are ineffective for this type of traffic.  Noisy   worms are easy to identify, but stealth worms can open a backdoor on   hosts and stay dormant for a long time without causing any noticeable   detrimental effect.  This type of bad traffic has the potential to   make the greatest impact on an enterprise from a threat perspective.   There are more mitigation tools available for enterprise networks   than for backbone and access network providers; one explanation might   be the greater affordability of solutions for enterprise networks.   The costs of damage from a security breach can also have a very   significant impact on the profits of an enterprise.  At the same   time, however, the workshop participants also expressed concerns   regarding the ongoing arms race between security exploits and   patching solutions.  Up to now, security efforts have, by and large,   been reactive, creating a chain of security exploits and a consequent   stream of "fixes".  Such a reactive mode has not only created a big   security market, but also does not enable us to get ahead of   attackers.3.4.  Domain Name Services   Different from backbone and access providers, there also exists a   class of Internet service infrastructure providers.  Provision of   Domain Name System (DNS) services offers an example here.  As   reported by operators from a major DNS hosting company, over time   there have been increasingly significant DDoS attacks on .com, .net   and root servers.   DNS service operators have witnessed large scale DDoS attacks.  The   most recent ones include reflection attacks resulting from queries   using spoofed source addresses.  The major damage caused by these   attacks are bandwidth and resource exhaustion, which led to   disruption of critical services.  The peak rate of daily DNS   transactions has been growing at a much faster rate than the number   of Internet users, and this trend is expected to continue.  The heavy   load on the DNS servers has led to increasing complexity in providing   the services.   In addition to intentional DDoS Attacks, some other causes of the   heavy DNS load included (1) well known bugs in a small number of DNS   servers that still run an old version of the BIND software, causing   significant load increase at top level servers; and (2)   inappropriately configured firewalls that allow DNS queries to come   out but block returning DNS replies, resulting in big adverse impacts   on the overall system.  Most of such issues have been addressed in   the DNS operational guidelines drafted by the IETF DNS OperationsAndersson, et al.            Informational                     [Page 14]

RFC 4948                    Unwanted Traffic                 August 2007   Working Group; however, many DNS operators have not taken appropriate   actions.   At this time, the only effective and viable mitigation approach is   over-engineering the DNS service infrastructure by increasing link   bandwidth, the number of servers, and the server processing power, as   well as deploying network anycast.  There is a concern about whether   the safety margin gained from over-engineering is, or is not,   adequate in sustaining DNS services over future attacks.  Looking   forward, there are also a few new issues looming.  Two imminent ones   are the expected widespread deployment of IPv6 whose new DNS software   would inevitably contain new bugs, and the DNS Security Extensions   (DNSSEC), which could potentially be abused to generate DDoS attacks.4.  Current Vulnerabilities and Existing Solutions   This section summarizes three aspects of the workshop discussions.   We first collected the major vulnerabilities mentioned in the   workshop, then made a summary of the existing solutions, and followed   up with an examination of the effectiveness, or lack of it, of the   existing solutions.4.1.  Internet Vulnerabilities   Below is a list of known Internet vulnerabilities and issues around   unwanted traffic.   o  Packet source address spoofing: there has been speculation that      attacks using spoofed source addresses are decreasing, due to the      proliferation of botnets, which can be used to launch various      attacks without using spoofed source addresses.  It is certainly      true that not all the attacks use spoofed addresses; however, many      attacks, especially reflection attacks, do use spoofed source      addresses.   o  BGP route hijacking: in a survey conducted by Arbor Networks,      route hijacking together with source address spoofing are listed      as the two most critical vulnerabilities on the Internet.  It has      been observed that miscreants hijack bogon prefixes for spam      message injections.  Such hijacks do not affect normal packet      delivery and thus have a low chance of being noticed.   o  Everything over HTTP: port scan attacks occur frequently in      today's Internet, looking for open TCP or UDP ports through which      to gain access to computers.  The reaction from computer system      management has been to close down all the unused ports, especially      in firewalls.  One result of this reaction is that application      designers have moved to transporting all data communications overAndersson, et al.            Informational                     [Page 15]

RFC 4948                    Unwanted Traffic                 August 2007      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 Solutions4.2.1.  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 wasBCP 38 on ingress filtering: universal deployment ofAndersson, et al.            Informational                     [Page 16]

RFC 4948                    Unwanted Traffic                 August 2007BCP 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 ofBCP 38 could benefit the   Internet as a whole, deployment by individual sites imposes a certain   amount of cost to the site, and does not provide a direct and   tangible benefit in return.  In other words,BCP 38 suffers from a   lack of deployment incentives.   Both BGP null routing and ACL have the drawback of relying on manual   configuration and thus are labor intensive.  In addition, they also   suffer from blocking both attack and legitimate packets.  There is   also a potential that some tools could back-fire, e.g., an overly   long ACL list might significantly slow down packet forwarding in a   router.   Unicast Reverse Path Filtering (uRPF), which is available on some   routers, provides a means of implementing a restricted form ofBCP 38   ingress filtering without the effort of maintaining ACLs. uRPF uses   the routing table to check that a valid path back to the source   exists.  However, its effectiveness depends on the specificity of the   routes against which source addresses are compared.  The prevalence   of asymmetric routing means that the strict uRPF test (where the   route to the source must leave from the same interface on which the   packet being tested arrived) may have to be replaced by the loose   uRPF test (where the route may leave from any interface).  The loose   uRPF test is not a guarantee against all cases of address spoofing,   and it may still be necessary to maintain an ACL to deal with   exceptions.4.2.2.  Existing Solutions for Enterprise Networks   A wide variety of commercial products is available for enterprise   network protection.  Three popular types of protection mechanisms are   o  Firewalls: firewalls are perhaps the most widely deployed      protection products.  However, the effectiveness of firewalls in      protecting enterprise confidential information can be weakened by      spyware installed internally, and they are ineffective against      attacks carried out from inside the perimeter established by the      firewalls.  Too often, spyware installation is a byproduct of      installing other applications permitted by end users.Andersson, et al.            Informational                     [Page 17]

RFC 4948                    Unwanted Traffic                 August 2007   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 Protection4.3.1.  Inadequate Tools   Generally speaking, network and service operators do not have   adequate tools for network problem diagnosis.  The current approaches   largely rely on the experience and skills of the operators, and on   time-consuming manual operations.  The same is true for mitigation   tools against attacks.4.3.2.  Inadequate Deployments   The limited number of existing Internet protection measures have not   been widely deployed.  Deployment of security solutions requires   resources which may not be available.  It also requires education   among the operational community to recognize the critical importance   of patch installation and software upgrades; for example, a bug in   the BIND packet was discovered and fixed in 2003, yet a number of DNS   servers still run the old software today.  Perhaps most importantly,   a security solution must be designed with the right incentives to   promote their deployment.  Effective protection also requires   coordination between competing network providers.  For the time   being, it is often difficult to even find the contact information for   operators of other networks.   A number of workshop participants shared the view that, if all the   known engineering approaches and bug fixes were universally deployed,   the Internet could have been enjoying a substantially reduced numberAndersson, et al.            Informational                     [Page 18]

RFC 4948                    Unwanted Traffic                 August 2007   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, andAndersson, et al.            Informational                     [Page 19]

RFC 4948                    Unwanted Traffic                 August 2007   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 inSection 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.Andersson, et al.            Informational                     [Page 20]

RFC 4948                    Unwanted Traffic                 August 20075.2.  Flow Based Tools   A set of tools based on flow data is widely used to extract   information from both network and data link layers.  Tools have been   built that can be used to find out the sources of almost any type of   traffic, including certain unwanted traffic.  These flow-based tools   make it possible to do things like DDoS traceback, traffic/peering   analyses, and detection of botnets, worms, and spyware.   These tools monitor flows on the network and build baselines for what   is the "normal" behavior.  Once the baseline is available, it is   possible to detect anomalous activity.  It is easy to detect   variations over time, and decide if the variation is legitimate or   not.  It is possible to take this approach further, typically   involving the identification of signatures of particular types of   traffic.   These flow-based tools are analogous to the "sonar" that is used by   navies to listen for submarines.  Once a particular submarine is   identified, it is possible to record its sonar signature to be used   to provide rapid identification in the future when the same submarine   is encountered again.   Examples of existing tools include   Cisco IOS NetFlow <http://www.cisco.com/en/US/products/ps6601/products_ios_protocol_group_home.html>,   sFlow <http://www.sflow.org/>, and   NeTraMet <http://www.caida.org/tools/measurement/netramet/> based on   the IETF RTFM and IPFIX standards.   There are also tools for working with the output of NetFlow such as   jFlow <http://www.net-track.ch/opensource/jflow/> and   Arbor Networks' Peakflow   <http://www.arbor.net/products_platform.php>.   The Cooperative Association for Internet Data Analysis (CAIDA)   maintains a taxonomy of available tools on its web site at   <http://www.caida.org/tools/taxonomy/index.xml>.5.3.  Internet Motion Sensor (IMS)   The Internet Motion Sensor (IMS) [IMS] may be used to watch traffic   to or from "Darknets" (routable prefixes that don't have end hosts   attached), unassigned address spaces, and unannounced address spaces.   By watching activities in these types of address spaces, one can   understand and detect, e.g., scanning activities, DDoS worms, worm   infected hosts, and misconfigured hosts.Andersson, et al.            Informational                     [Page 21]

RFC 4948                    Unwanted Traffic                 August 2007   Currently, the IMS is used to monitor approximately 17 million   prefixes, about 1.2% of the IPv4 address space.  The use of IMS has   highlighted two major characteristics of attacks; malicious attacks   are more targeted than one might have assumed, and a vulnerability in   a system does not necessarily lead to a threat to that system (e.g.,   the vulnerability may not be exploited to launch attacks if the   perceived "benefit" to the attacker appears small).  Data from IMS   and other sources indicates that attackers are making increased use   of information from social networking sites to target their attacks   and select perceived easy targets, such as computers running very old   versions of systems or new, unpatched vulnerabilities.   This form of passive data collection is also known as a "Network   Telescope".  Links to similar tools can be found on the CAIDA web   site at <http://www.caida.org/data/passive/network_telescope.xml>.5.4.BCP 38   In the year 2000, the IETF developed a set of recommendations to   limit DOS attacks and Address Spoofing published asBCP 38 [RFC2827],   "Network Ingress Filtering: Defeating Denial of Service Attacks which   employ IP Source Address Spoofing".  However, up to nowBCP 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   extendingBCP 38 to multihomed networks.  These recommendations are   published asBCP 84 [RFC3704].5.5.  Layer 5 to 7 Awareness   Tools are being developed that will make it possible to perform deep   packet inspection at high speed.  Some companies are working on   hardware implementation to inspect all layers from 2 to 7 (e.g.,   EZchip <http://www.ezchip.com/t_npu_whpaper.htm>).  A number of other   companies, including Cisco and Juniper, offer tools capable of   analyzing packets at the transport layer and above.5.6.  How To's   One idea that was discussed at the workshop envisaged operators and   standards bodies cooperating to produce a set of "How To" documents   as guidelines on how to configure networks.  Dissemination and use of   these "How To's" should be encouraged by vendors, operators, and   standards bodies.Andersson, et al.            Informational                     [Page 22]

RFC 4948                    Unwanted Traffic                 August 2007   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 inAppendix C).6.1.  Ongoing ResearchSection 6.1 discusses briefly areas where we see active research on   unwanted traffic today.6.1.1.  Exploited Hosts   One area where researchers are very active is analyzing situations   where hosts are exploited.  This has been a major focus for a long   time, and an abundance of reports have been published.  Current   research may be divided into three different categories: prevention,   detection, and defense.6.1.1.1.  Prevention   Code quality is crucial when it comes to preventing exploitation of   Internet hosts.  Quite a bit of research effort has therefore gone   into improvement of code quality.  Researchers are looking into   automated methods for finding bugs and maybe in the end fixes for any   bugs detected.   A second approach designed to stop hosts from becoming compromised is   to reduce the "attack surface".  Researchers are thinking aboutAndersson, et al.            Informational                     [Page 23]

RFC 4948                    Unwanted Traffic                 August 2007   changes or extensions to the Internet architecture.  The idea is to   create a strict client server architecture, where the clients only   are allowed to initiate connections, and while servers may only   accept connections.   Researchers have put a lot of effort into better scaling of honey   pots and honey farms to better understand and neutralize the methods   miscreants are using to exploit hosts.  Research also goes into   developing honey monkeys in order to understand how hosts are   vulnerable.  Both honey pots/farms and honey monkeys are aimed at   taking measures that prevent further (mis-)use of possible exploits.6.1.1.2.  Detection   When an attack is launched against a computer system, the attack   typically leaves evidence of the intrusion in the system logs.  Each   type of intrusion leaves a specific kind of footprint or signature.   The signature can be evidence that certain software has been   executed, that logins have failed, that administrative privileges   have been misused, or that particular files and directories have been   accessed.  Administrators can document these attack signatures and   use them to detect the same type of attack in the future.  This   process can be automated.   Because each signature is different, it is possible for system   administrators to determine by looking at the intrusion signature   what the intrusion was, how and when it was perpetrated, and even how   skilled the intruder is.   Once an attack signature is available, it can be used to create a   vulnerability filter, i.e., the stored attack signature is compared   to actual events in real time and an alarm is given when this pattern   is repeated.   A further step may be taken with automated vulnerability signatures,   i.e., when a new type of attack is found, a vulnerability filter is   automatically created.  This vulnerability filter can be made   available for nodes to defend themselves against this new type of   attack.  The automated vulnerability signatures may be part of an   Intrusion Detection System (IDS).6.1.1.3.  Defense   An IDS can be a part of the defense against actual attacks, e.g., by   using vulnerability filters.  An Intrusion Detection System (IDS)   inspects inbound and outbound network activities and detects   signatures that indicate that a system is under attack from someone   attempting to break into or compromise the system.Andersson, et al.            Informational                     [Page 24]

RFC 4948                    Unwanted Traffic                 August 20076.1.2.  Distributed Denial of Service (DDoS) Attacks   Research on DDoS attacks follows two separate approaches, the first   has the application as its focus, while the second focuses on the   network.6.1.2.1.  Application Oriented DDoS Research   The key issue with application oriented research is to distinguish   between legitimate activities and attacks.  Today, several tools   exist that can do this and research has moved on to more advanced   things.   Research today looks into tools that can detect and filter activities   that have been generated by bots and botnets.   One approach is to set up a tool that sends challenges to senders   that want to send traffic to a certain node.  The potential sender   then has to respond correctly to that challenge; otherwise, the   traffic will be filtered out.   The alternative is to get more capacity between sender and receiver.   This is done primarily by some form of use of peer-to-peer   technology.   Today, there is "peer-to-peer hype" in the research community; a sure   way of making yourself known as a researcher is to publish something   that solves old problems by means of some peer-to-peer technology.   Proposals now exist for peer-to-peer DNS, peer-to-peer backup   solutions, peer-to-peer web-cast, etc.  Whether these proposals can   live up to the hype remains to be seen.6.1.2.2.  Network Oriented DDoS Research   Research on DDoS attacks that takes a network oriented focus may be   described by the following oversimplified three steps.   1.  Find the bad stuff   2.  Set the "evil bit" on those packets   3.  Filter out the packets with the "evil bit" set   This rather uncomplicated scheme has to be carried out on high-speed   links and interfaces.  Automation is the only way of achieving this.   One way of indirectly setting the "evil bit" is to use a normalized   TTL.  The logic goes: the TTL for traffic from this sender has alwaysAndersson, et al.            Informational                     [Page 25]

RFC 4948                    Unwanted Traffic                 August 2007   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.Andersson, et al.            Informational                     [Page 26]

RFC 4948                    Unwanted Traffic                 August 20076.1.5.  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 inAndersson, et al.            Informational                     [Page 27]

RFC 4948                    Unwanted Traffic                 August 2007   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 previouslyAndersson, et al.            Informational                     [Page 28]

RFC 4948                    Unwanted Traffic                 August 2007   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 theAndersson, et al.            Informational                     [Page 29]

RFC 4948                    Unwanted Traffic                 August 2007   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, andRFC 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.Andersson, et al.            Informational                     [Page 30]

RFC 4948                    Unwanted Traffic                 August 2007   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 applyAndersson, et al.            Informational                     [Page 31]

RFC 4948                    Unwanted Traffic                 August 2007      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.Andersson, et al.            Informational                     [Page 32]

RFC 4948                    Unwanted Traffic                 August 20078.3.  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] andBCP 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.Andersson, et al.            Informational                     [Page 33]

RFC 4948                    Unwanted Traffic                 August 2007   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.Andersson, et al.            Informational                     [Page 34]

RFC 4948                    Unwanted Traffic                 August 2007   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.Andersson, et al.            Informational                     [Page 35]

RFC 4948                    Unwanted Traffic                 August 2007   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 byRFC 1459   [RFC1459] but much improved and extended since its original   invention.  IRC clients rendezvous and exchange messages through IRC   servers.  IRC servers are run by many organizations for both benign   and nefarious purposes.   Malware   Malware is software designed to infiltrate or damage a computer   system, without the owner's informed consent.  There are   disagreements about the etymology of the term itself, the primary   uncertainty being whether it is a portmanteau word (of "malicious"   and "software") or simply composed of the prefix "mal-" and the   morpheme "ware".  Malware references the intent of the creator,   rather than any particular features.  It includes computer viruses,   worms, Trojan horses, spyware, adware, and other malicious and   unwanted software.  In law, malware is sometimes known as a computer   contaminant.   Mix networks   Mix networks create hard-to-trace communications by using a chain of   proxy servers [MIX].  Each message is encrypted to each proxy; the   resulting encryption is layered like a Russian doll with the message   as the innermost layer.  Even if all but one of the proxies are   compromised by a tracer, untraceability is still achieved.  More   information can be found at   <http://www.adastral.ucl.ac.uk/~helger/crypto/link/protocols/mix.php>.Andersson, et al.            Informational                     [Page 36]

RFC 4948                    Unwanted Traffic                 August 2007   Onion routing   Onion routing is a technique for anonymous communication over a   computer network, it is a technique that encodes routing information   in a set of encrypted layers.  Onion routing is based on mix cascades   (see mix networks (q.v.)).  More information can be found at   <http://www.onion-router.net/>.   Phishing   Phishing is a form of criminal activity using social engineering   techniques.  It is characterized by attempts to fraudulently acquire   sensitive information, such as passwords and credit card details, by   masquerading as a trustworthy person or business in an apparently   official electronic communication.  Phishing is typically carried out   using spoofed websites, email, or an instant message.  The term   phishing derives from password harvesting and the use of increasingly   sophisticated lures to "fish" for users' financial information and   passwords.   Root access   Access to a system with full administrative privileges bypassing any   security restrictions placed on normal users.  Derived from the name   traditionally used for the 'superuser' on Unix systems.   Script kiddy   Derogatory term for an inexperienced hacker who mindlessly uses   scripts and other programs developed by others with the intent of   compromising computers or generating DoS attacks.   Spam   Spamming is the abuse of electronic messaging systems to send   unsolicited, undesired bulk messages.  The individual messages are   refereed to as spam.  The term is frequently used to refer   specifically to the electronic mail form of spam.   Spoofing   (IP) spoofing is a technique where the illegitimate source of IP   packets is obfuscated by contriving to use IP address(es) that the   receiver recognizes as a legitimate source.  Spoofing is often used   to gain unauthorized access to computers or mislead filtering   mechanisms, whereby the intruder sends packets into the network with   an IP source address indicating that the message is coming from a   legitimate host.  To engage in IP spoofing, a hacker must first use a   variety of techniques to find an IP address of a valid host and then   modify the packet headers so that it appears that the packets are   coming from that host.Andersson, et al.            Informational                     [Page 37]

RFC 4948                    Unwanted Traffic                 August 2007   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 inAppendix 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 IABAndersson, et al.            Informational                     [Page 38]

RFC 4948                    Unwanted Traffic                 August 2007   especially appreciates the effort of those that prepared and made   presentations at the workshop.12.  Informative References   [IMS]      University of Michigan, "Internet Motion Sensor", 2006,              <http://ims.eecs.umich.edu/>.   [IRR]      Merit Network Inc, "Internet Routing Registry Routing              Assets Database", 2006, <http://www.irr.net/>.   [MIX]      Hill, R., Hwang, A., and D. Molnar, "Approaches to Mix              Nets", MIT 6.857 Final Project, December 1999, <http://www.mit.edu/afs/athena/course/6/6.857/OldStuff/Fall99/papers/mixnet.ps.gz>.   [RFC1122]  Braden, R., "Requirements for Internet Hosts -              Communication Layers", STD 3,RFC 1122, October 1989.   [RFC1123]  Braden, R., "Requirements for Internet Hosts - Application              and Support", STD 3,RFC 1123, October 1989.   [RFC1459]  Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol",RFC 1459, May 1993.   [RFC1812]  Baker, F., "Requirements for IP Version 4 Routers",RFC 1812, June 1995.   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and              E. Lear, "Address Allocation for Private Internets",BCP 5,RFC 1918, February 1996.   [RFC2142]  Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND              FUNCTIONS",RFC 2142, May 1997.   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:              Defeating Denial of Service Attacks which employ IP Source              Address Spoofing",BCP 38,RFC 2827, May 2000.   [RFC3330]  IANA, "Special-Use IPv4 Addresses",RFC 3330,              September 2002.   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed              Networks",BCP 84,RFC 3704, March 2004.   [SHRED]    Krishnamurthy, B. and E. Blackmond, "SHRED: Spam              Harassment Reduction via Economic Disincentives", 2003,              <http://www.research.att.com/~bala/papers/shred-ext.ps>.Andersson, et al.            Informational                     [Page 39]

RFC 4948                    Unwanted Traffic                 August 2007Appendix 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)Andersson, et al.            Informational                     [Page 40]

RFC 4948                    Unwanted Traffic                 August 2007Appendix B.  Workshop Agenda   Session 1:   How bad is the problem? What are the most important symptoms?   Session 2:   What are the sources of the problem?   Lunch session (session 3):   Solutions in regulatory and societal space   Session 4:   The underground economy   Session 5:   Current countermeasures, what works, what doesn't   Session 6:   If all our wishes could be granted, what would they be?   Session 7:   What's in the pipeline, or should be in the pipeline   Session 8:   What is being actively researched on?   Session 9:   What are the engineering (immediate and longer term) and   research issues that might be pursued within the IETF/IAB/IRTF?Appendix C.  Slides   Links to a subset of the presentations given by the participants at   the workshop can be found via the IAB Workshops page on the IAB web   site at <http://utgard.ietf.org/iab/about/workshops/unwantedtraffic/index.html>.  As mentioned inSection 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.Andersson, et al.            Informational                     [Page 41]

RFC 4948                    Unwanted Traffic                 August 2007Authors' Addresses   Loa Andersson   Acreo AB   EMail: loa@pi.se   Elwyn Davies   Folly Consulting   EMail: elwynd@dial.pipex.com   Lixia Zhang   UCLA   EMail: lixia@cs.ucla.eduAndersson, et al.            Informational                     [Page 42]

RFC 4948                    Unwanted Traffic                 August 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Andersson, et al.            Informational                     [Page 43]