Internet Engineering Task Force (IETF)                        S. Farrell
Request for Comments: 7258                        Trinity College Dublin
BCP: 188                                                   H. Tschofenig
Category: Best Current Practice                                 ARM Ltd.
ISSN: 2070-1721                                                 May 2014

                   Pervasive Monitoring Is an Attack


   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 in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 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.

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1.  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

   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.

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2.  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 of RFC 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

   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

   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-spam

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   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.

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5.  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

              IETF, "IETF 88 Plenary Meeting Materials", November 2013,

   [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

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July

   [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", RFC
              4949, 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.

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   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973, July

Authors' Addresses

   Stephen Farrell
   Trinity College Dublin
   Dublin  2

   Phone: +353-1-896-2354
   EMail: stephen.farrell@cs.tcd.ie

   Hannes Tschofenig
   ARM Ltd.
   6060 Hall in Tirol

   EMail: Hannes.tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at

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