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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
 ( 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 2014

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.

Farrell & Tschofenig Best Current Practice [Page 2] RFC 7258 Pervasive Monitoring Is an Attack May 2014

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

Farrell & 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 2014

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 and the 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.

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

Authors' Addresses

 Stephen Farrell
 Trinity College Dublin
 Dublin  2
 Phone: +353-1-896-2354
 Hannes Tschofenig
 ARM Ltd.
 6060 Hall in Tirol

Farrell & Tschofenig Best Current Practice [Page 6]

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