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Internet Engineering Task Force (IETF)                        S. FarrellRequest for Comments: 7258                        Trinity College DublinBCP: 188                                                   H. TschofenigCategory: Best Current Practice                                 ARM Ltd.ISSN: 2070-1721                                                 May 2014Pervasive Monitoring Is an AttackAbstract   Pervasive monitoring is a technical attack that should be mitigated   in the design of IETF protocols, where possible.Status of This Memo   This memo documents an Internet Best Current Practice.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   BCPs is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7258.Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Farrell & Tschofenig      Best Current Practice                 [Page 1]

RFC 7258            Pervasive Monitoring Is an Attack           May 20141.  Pervasive Monitoring Is a Widespread Attack on Privacy   Pervasive Monitoring (PM) is widespread (and often covert)   surveillance through intrusive gathering of protocol artefacts,   including application content, or protocol metadata such as headers.   Active or passive wiretaps and traffic analysis, (e.g., correlation,   timing or measuring packet sizes), or subverting the cryptographic   keys used to secure protocols can also be used as part of pervasive   monitoring.  PM is distinguished by being indiscriminate and very   large scale, rather than by introducing new types of technical   compromise.   The IETF community's technical assessment is that PM is an attack on   the privacy of Internet users and organisations.  The IETF community   has expressed strong agreement that PM is an attack that needs to be   mitigated where possible, via the design of protocols that make PM   significantly more expensive or infeasible.  Pervasive monitoring was   discussed at the technical plenary of the November 2013 IETF meeting   [IETF88Plenary] and then through extensive exchanges on IETF mailing   lists.  This document records the IETF community's consensus and   establishes the technical nature of PM.   The term "attack" is used here in a technical sense that differs   somewhat from common English usage.  In common English usage, an   attack is an aggressive action perpetrated by an opponent, intended   to enforce the opponent's will on the attacked party.  The term is   used here to refer to behavior that subverts the intent of   communicating parties without the agreement of those parties.  An   attack may change the content of the communication, record the   content or external characteristics of the communication, or through   correlation with other communication events, reveal information the   parties did not intend to be revealed.  It may also have other   effects that similarly subvert the intent of a communicator.   [RFC4949] contains a more complete definition for the term "attack".   We also use the term in the singular here, even though PM in reality   may consist of a multifaceted set of coordinated attacks.   In particular, the term "attack", used technically, implies nothing   about the motivation of the actor mounting the attack.  The   motivation for PM can range from non-targeted nation-state   surveillance, to legal but privacy-unfriendly purposes by commercial   enterprises, to illegal actions by criminals.  The same techniques to   achieve PM can be used regardless of motivation.  Thus, we cannot   defend against the most nefarious actors while allowing monitoring by   other actors no matter how benevolent some might consider them to be,   since the actions required of the attacker are indistinguishable from   other attacks.  The motivation for PM is, therefore, not relevant for   how PM is mitigated in IETF protocols.Farrell & Tschofenig      Best Current Practice                 [Page 2]

RFC 7258            Pervasive Monitoring Is an Attack           May 20142.  The IETF Will Work to Mitigate Pervasive Monitoring   "Mitigation" is a technical term that does not imply an ability to   completely prevent or thwart an attack.  Protocols that mitigate PM   will not prevent the attack but can significantly change the threat.   (See the diagram on page 24 ofRFC 4949 for how the terms "attack"   and "threat" are related.)  This can significantly increase the cost   of attacking, force what was covert to be overt, or make the attack   more likely to be detected, possibly later.   IETF standards already provide mechanisms to protect Internet   communications and there are guidelines [RFC3552] for applying these   in protocol design.  But those standards generally do not address PM,   the confidentiality of protocol metadata, countering traffic   analysis, or data minimisation.  In all cases, there will remain some   privacy-relevant information that is inevitably disclosed by   protocols.  As technology advances, techniques that were once only   available to extremely well-funded actors become more widely   accessible.  Mitigating PM is therefore a protection against a wide   range of similar attacks.   It is therefore timely to revisit the security and privacy properties   of our standards.  The IETF will work to mitigate the technical   aspects of PM, just as we do for protocol vulnerabilities in general.   The ways in which IETF protocols mitigate PM will change over time as   mitigation and attack techniques evolve and so are not described   here.   Those developing IETF specifications need to be able to describe how   they have considered PM, and, if the attack is relevant to the work   to be published, be able to justify related design decisions.  This   does not mean a new "pervasive monitoring considerations" section is   needed in IETF documentation.  It means that, if asked, there needs   to be a good answer to the question "Is pervasive monitoring relevant   to this work and if so, how has it been considered?"   In particular, architectural decisions, including which existing   technology is reused, may significantly impact the vulnerability of a   protocol to PM.  Those developing IETF specifications therefore need   to consider mitigating PM when making architectural decisions.   Getting adequate, early review of architectural decisions including   whether appropriate mitigation of PM can be made is important.   Revisiting these architectural decisions late in the process is very   costly.   While PM is an attack, other forms of monitoring that might fit the   definition of PM can be beneficial and not part of any attack, e.g.,   network management functions monitor packets or flows and anti-spamFarrell & Tschofenig      Best Current Practice                 [Page 3]

RFC 7258            Pervasive Monitoring Is an Attack           May 2014   mechanisms need to see mail message content.  Some monitoring can   even be part of the mitigation for PM, for example, certificate   transparency [RFC6962] involves monitoring Public Key Infrastructure   in ways that could detect some PM attack techniques.  However, there   is clear potential for monitoring mechanisms to be abused for PM, so   this tension needs careful consideration in protocol design.  Making   networks unmanageable to mitigate PM is not an acceptable outcome,   but ignoring PM would go against the consensus documented here.  An   appropriate balance will emerge over time as real instances of this   tension are considered.   Finally, the IETF, as a standards development organisation, does not   control the implementation or deployment of our specifications   (though IETF participants do develop many implementations), nor does   the IETF standardise all layers of the protocol stack.  Moreover, the   non-technical (e.g., legal and political) aspects of mitigating   pervasive monitoring are outside of the scope of the IETF.  The   broader Internet community will need to step forward to tackle PM, if   it is to be fully addressed.   To summarise: current capabilities permit some actors to monitor   content and metadata across the Internet at a scale never before   seen.  This pervasive monitoring is an attack on Internet privacy.   The IETF will strive to produce specifications that mitigate   pervasive monitoring attacks.3.  Process Note   In the past, architectural statements of this sort, e.g., [RFC1984]   and [RFC2804], have been published as joint products of the Internet   Engineering Steering Group (IESG) and the Internet Architecture Board   (IAB).  However, since those documents were published, the IETF and   IAB have separated their publication "streams" as described in   [RFC4844] and [RFC5741].  This document was initiated after   discussions in both the IESG and IAB, but is published as an IETF-   stream consensus document, in order to ensure that it properly   reflects the consensus of the IETF community as a whole.4.  Security Considerations   This document is entirely about privacy.  More information about the   relationship between security and privacy threats can be found in   [RFC6973].Section 5.1.1 of [RFC6973] specifically addresses   surveillance as a combined security-privacy threat.Farrell & Tschofenig      Best Current Practice                 [Page 4]

RFC 7258            Pervasive Monitoring Is an Attack           May 20145.  Acknowledgements   We would like to thank the participants of the IETF 88 technical   plenary for their feedback.  Thanks in particular to the following   for useful suggestions or comments: Jari Arkko, Fred Baker, Marc   Blanchet, Tim Bray, Scott Brim, Randy Bush, Brian Carpenter, Benoit   Claise, Alissa Cooper, Dave Crocker, Spencer Dawkins, Avri Doria,   Wesley Eddy, Adrian Farrel, Joseph Lorenzo Hall, Phillip   Hallam-Baker, Ted Hardie, Sam Hartmann, Paul Hoffman, Bjoern   Hoehrmann, Russ Housley, Joel Jaeggli, Stephen Kent, Eliot Lear,   Barry Leiba, Ted Lemon, Subramanian Moonesamy, Erik Nordmark, Pete   Resnick, Peter Saint-Andre, Andrew Sullivan, Sean Turner, Nicholas   Weaver, Stefan Winter, and Lloyd Wood.  Additionally, we would like   to thank all those who contributed suggestions on how to improve   Internet security and privacy or who commented on this on various   IETF mailing lists, such as the ietf@ietf.org and the   perpass@ietf.org lists.6.  Informative References   [IETF88Plenary]              IETF, "IETF 88 Plenary Meeting Materials", November 2013,              <http://www.ietf.org/proceedings/88/>.   [RFC1984]  IAB, IESG, Carpenter, B., and F. Baker, "IAB and IESG              Statement on Cryptographic Technology and the Internet",RFC 1984, August 1996.   [RFC2804]  IAB and IESG, "IETF Policy on Wiretapping",RFC 2804, May              2000.   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC              Text on Security Considerations",BCP 72,RFC 3552, July              2003.   [RFC4844]  Daigle, L. and Internet Architecture Board, "The RFC              Series and RFC Editor",RFC 4844, July 2007.   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",RFC4949, August 2007.   [RFC5741]  Daigle, L., Kolkman, O., and IAB, "RFC Streams, Headers,              and Boilerplates",RFC 5741, December 2009.   [RFC6962]  Laurie, B., Langley, A., and E. Kasper, "Certificate              Transparency",RFC 6962, June 2013.Farrell & Tschofenig      Best Current Practice                 [Page 5]

RFC 7258            Pervasive Monitoring Is an Attack           May 2014   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,              Morris, J., Hansen, M., and R. Smith, "Privacy              Considerations for Internet Protocols",RFC 6973, July              2013.Authors' Addresses   Stephen Farrell   Trinity College Dublin   Dublin  2   Ireland   Phone: +353-1-896-2354   EMail: stephen.farrell@cs.tcd.ie   Hannes Tschofenig   ARM Ltd.   6060 Hall in Tirol   Austria   EMail: Hannes.tschofenig@gmx.net   URI:http://www.tschofenig.priv.atFarrell & Tschofenig      Best Current Practice                 [Page 6]