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Network Working Group                                         S. FarrellInternet-Draft                                    Trinity College DublinIntended status: Informational                              July 6, 2019Expires: January 7, 2020We're gonna need a bigger threat modeldraft-farrell-etm-03Abstract   We argue that an expanded threat model is needed for Internet   protocol development as protocol endpoints can no longer be   considered to be generally trustworthy for any general definition of   "trustworthy."Status of This Memo   This Internet-Draft is submitted in full conformance with the   provisions ofBCP 78 andBCP 79.   Internet-Drafts are working documents of the Internet Engineering   Task Force (IETF).  Note that other groups may also distribute   working documents as Internet-Drafts.  The list of current Internet-   Drafts is athttps://datatracker.ietf.org/drafts/current/.   Internet-Drafts are draft documents valid for a maximum of six months   and may be updated, replaced, or obsoleted by other documents at any   time.  It is inappropriate to use Internet-Drafts as reference   material or to cite them other than as "work in progress."   This Internet-Draft will expire on January 7, 2020.Copyright Notice   Copyright (c) 2019 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   (https://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                  Expires January 7, 2020                [Page 1]

Internet-Draft                     etm                         July 2019Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .3   2.  Examples of deliberate adversarial behaviour in applications    42.1.  Malware in curated application stores . . . . . . . . . .42.2.  Virtual private networks (VPNs) . . . . . . . . . . . . .52.3.  Compromised (home) networks . . . . . . . . . . . . . . .52.4.  Web browsers  . . . . . . . . . . . . . . . . . . . . . .52.5.  Web site policy deception . . . . . . . . . . . . . . . .52.6.  Tracking bugs in mail . . . . . . . . . . . . . . . . . .62.7.  Troll farms in online social networks . . . . . . . . . .62.8.  Smart televisions . . . . . . . . . . . . . . . . . . . .62.9.  So-called Internet of things  . . . . . . . . . . . . . .7     2.10. Attacks leveraging compromised high-level DNS           infrastructure  . . . . . . . . . . . . . . . . . . . . .72.11. BGP hijacking . . . . . . . . . . . . . . . . . . . . . .83.  Inadvertent adversarial behaviours  . . . . . . . . . . . . .84.  Possible directions for an expanded threat model  . . . . . .94.1.  Develop a BCP for privacy considerations  . . . . . . . .104.2.  Consider the user perspective . . . . . . . . . . . . . .104.3.  Consider ABuse-cases as well as use-cases . . . . . . . .104.4.  Re-consider protocol design "lore"  . . . . . . . . . . .104.5.  Isolation . . . . . . . . . . . . . . . . . . . . . . . .104.6.  Transparency  . . . . . . . . . . . . . . . . . . . . . .114.7.  Minimise  . . . . . . . . . . . . . . . . . . . . . . . .114.8.  Same-Origin Policy  . . . . . . . . . . . . . . . . . . .114.9.  Greasing  . . . . . . . . . . . . . . . . . . . . . . . .114.10. Generalise OAuth Threat Model . . . . . . . . . . . . . .124.11. One (or more) endpoint may be compromised . . . . . . . .124.12. Look again at how well we're securing infrastructure  . .12     4.13. Consider recovery from attack as part of protocol design   134.14. Don't think in terms of hosts . . . . . . . . . . . . . .135.  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .136.  Security Considerations . . . . . . . . . . . . . . . . . . .147.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .148.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .149.  References  . . . . . . . . . . . . . . . . . . . . . . . . .149.1.  Informative References  . . . . . . . . . . . . . . . . .149.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .18Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .19A.1.  Changes from -02 to -03 . . . . . . . . . . . . . . . . .19A.2.  Changes from -01 to -02 . . . . . . . . . . . . . . . . .19A.3.  Changes from -00 to -01 . . . . . . . . . . . . . . . . .20   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .20Farrell                  Expires January 7, 2020                [Page 2]

Internet-Draft                     etm                         July 20191.  Introduction   [[There's a github repo for this -- issues and PRs are welcome there.   <https://github.com/sftcd/etm> ]][RFC3552], Section 3 defines an "Internet Threat Model" which has   been commonly used when developing Internet protocols.  That assumes   that "the end-systems engaging in a protocol exchange have not   themselves been compromised."RFC 3552 is a formal part of of the   IETF's process as it is alsoBCP72.   SinceRFC 3552 was written, we have seen a greater emphasis on   considering privacy and [RFC6973] provides privacy guidance for   protocol developers.RFC 6973 is not a formal BCP, but appears to   have been useful for protocol developers as it is referenced by 38   later RFCs at the time of writing [1].BCP188, [RFC7258] subsequently recognised pervasive monitoring as a   particular kind of attack and has also been relatively widely   referenced (39 RFCs at the time of writing [2]).  To date, perhaps   most documents referencingBCP188 have considered state-level or in-   network adversaries.   In this document, we argue that we need to epxand our threat model to   acknowledge that today many applications are themselves rightly   considered potential adversaries for at least some relevant actors.   However, those (good) actors cannot in general refuse to communicate   and will with non-negligible probability encounter applications that   are adversarial.   We also argue that not recognising this reality causes Internet   protocol designs to sometimes fail to protect the systems and users   who depend on those.   Discussion related to expanding our concept of threat-model ought not   (but perhaps inevitably will) involve discussion of weakening how   confidentiality is provided in Internet protocols.  Whilst it may   superficially seem to be the case that encouraging in-network   interception could help with detection of adversarial application   behaviours, such a position is clearly mistaken once one notes that   adding middleboxes that can themselves be adversarial cannot be a   solution to the problem of possibly encountering adversarial code on   the network.  It is also the case that the IETF has rough consensus   to provide better, and not weaker, security and privacy, which   includes confidentiality services.  The IETF has maintained that   consensus over three decades, despite repeated (and repetitive;-)   debates on the topic.  That consensus is represented in [RFC2804],BCP 200 [RFC1984] and more latterly, the above-mentionedBCP 188 asFarrell                  Expires January 7, 2020                [Page 3]

Internet-Draft                     etm                         July 2019   well as in the numerous RFCs referencing those works.  The   probability that discussion of expanding our threat model leads to a   change in that rough consensus seems highly remote.   However, it is not clear if the IETF will reach rough consensus on a   description of such an expanded threat model.  We argue that ignoring   this aspect of deployed reality may not bode well for Internet   protocol development.   Absent such an expanded threat model, we expect to see more of a   mismatch between expectaions and the deployment reality for some   Internet protocols.   Version -02 of this internet-draft was a submission to the IAB's DEDR   workshop [3].  We note that another author independently proposed   changes to the Internet threat model for related, but different,   reasons, [I-D.arkko-arch-internet-threat-model] also as a submission   to the DEDR workshop.   We are saddened by, and apologise for, the somewhat dystopian   impression that this document may impart - hopefully, there's a bit   of hope at the end;-)2.  Examples of deliberate adversarial behaviour in applications   In this section we describe a few documented examples of deliberate   adversarial behaviour by applications that could affect Internet   protocol development.  The adversarial behaviours described below   involve various kinds of attack, varying from simple fraud, to   credential theft, surveillance and contributing to DDoS attacks.   This is not intended to be a comprehensive nor complete survey, but   to motivate us to consider deliberate adversarial behaviour by   applications.   While we have these examples of deliberate adversarial behaviour,   there are also many examples of application developers doing their   best to protect the security and privacy of their users or customers.   That's just the same as the case today where we need to consider in-   network actors as potential adversaries despite the many examples of   network operators who do act primarily in the best interests of their   users.  So this section is not intended as a slur on all or some   application developers.2.1.  Malware in curated application stores   Despite the best efforts of curators, so-called App-Stores frequently   distribute malware of many kinds and one recent study [curated]   claims that simple obfuscation enables malware to avoid detection byFarrell                  Expires January 7, 2020                [Page 4]

Internet-Draft                     etm                         July 2019   even sophisticated operators.  Given the scale of these deployments,   ditribution of even a small percentage of malware-infected   applictions can affect a huge number of people.2.2.  Virtual private networks (VPNs)   Virtual private networks (VPNs) are supposed to hide user traffic to   various degrees depending on the particular technology chosen by the   VPN provider.  However, not all VPNs do what they say, some for   example misrepresenting the countries in which they provide vantage   points. [vpns]2.3.  Compromised (home) networks   What we normally might consider network devices such as home routers   do also run applications that can end up being adversarial, for   example running DNS and DHCP attacks from home routers targeting   other devices in the home.  One study [home] reports on a 2011 attack   that affected 4.5 million DSL modems in Brazil.  The absence of   software update [RFC8240] has been a major cause of these issues and   rises to the level that considering this as intentional behaviour by   device vendors who have chosen this path is warranted.2.4.  Web browsers   Tracking of users in order to support advertising based business   models is ubiquitous on the Internet today.  HTTP header fields (such   as cookies) are commonly used for such tracking, as are structures   within the content of HTTP responses such as links to 1x1 pixel   images and (ab)use of Javascript APIs offered by browsers. [tracking]   While some people may be sanguine about this kind of tracking, others   consider this behaviour unwelcome, when or if they are informed that   it happens, [attitude] though the evidence here seems somewhat harder   to interpret and many studies (that we have found to date) involve   small numbers of users.  Historically, browsers have not made this   kind of tracking visible and have enabled it by default, though some   recent browser versions are starting to enable visibility and   blocking of some kinds of tracking.  Browsers are also increasingly   imposing more stringent requirements on plug-ins for varied security   reasons.2.5.  Web site policy deception   Many web sites today provide some form of privacy policy and terms of   service, that are known to be mostly unread. [unread] This implies   that, legal fiction aside, users of those sites have not in reality   agreed to the specific terms published and so users are thereforeFarrell                  Expires January 7, 2020                [Page 5]

Internet-Draft                     etm                         July 2019   highly exposed to being exploited by web sites, for example   [cambridge] is a recent well-publicised case where a service provider   abused the data of 87 million users via a partnership.  While many   web site operators claim that they care deeply about privacy, it   seems prudent to assume that some (or most?) do not in fact care   about user privacy, or at least not in ways with which many of their   users would agree.  And of course, today's web sites are actually   mostly fairly complex web applications and are no longer static sets   of HTML files, so calling these "web sites" is perhaps a misnomer,   but considered as web applications, that may for example link in   advertising networks, it seems clear that many exist that are   adversarial.2.6.  Tracking bugs in mail   Some mail user agents (MUAs) render HTML content by default (with a   subset not allowing that to be turned off, perhaps particularly on   mobile devices) and thus enable the same kind of adversarial tracking   seen on the web.  Attempts at such intentional tracking are also seen   many times per day by email users - in one study [mailbug] the   authors estimated that 62% of leakage to third parties was   intentional, for example if leaked data included a hash of the   recipient email address.2.7.  Troll farms in online social networks   Online social network applications/platforms are well-known to be   vulnerable to troll farms, sometimes with tragic consequences, [4]   where organised/paid sets of users deliberately abuse the application   platform for reasons invisible to a normal user.  For-profit   companies building online social networks are well aware that subsets   of their "normal" users are anything but.  In one US study, [troll]   sets of troll accounts were roughly equally distributed on both sides   of a controversial discussion.  While Internet protocol designers do   sometimes consider sybil attacks [sybil], arguably we have not   provided mechanisms to handle such attacks sufficiently well,   especially when they occur within walled-gardens.  Equally, one can   make the case that some online social networks, at some points in   their evolution, appear to have prioritised counts of active users so   highly that they have failed to invest sufficient effort for   detection of such troll farms.2.8.  Smart televisions   There have been examples of so-called "smart" televisions spying on   their owners without permission [5] and one survey of user attitudes   [smarttv] found "broad agreement was that it is unacceptable for the   data to be repurposed or shared" although the level of userFarrell                  Expires January 7, 2020                [Page 6]

Internet-Draft                     etm                         July 2019   understanding may be questionable.  What is clear though is that such   devices generally have not provided controls for their owners that   would allow them to meaningfully make a decision as to whether or not   they want to share such data.2.9.  So-called Internet of things   Many so-called Internet of Things (IoT) devices ("so-called" as all   devices were already things:-) have been found extremely deficient   when their security and privacy aspects were analysed, for example   children's toys. [toys] While in some cases this may be due to   incompetence rather than being deliberately adversarial behaviour,   the levels of incompetence frequently seen imply that it is valid to   consider such cases as not being accidental.2.10.  Attacks leveraging compromised high-level DNS infrastructure   Recent attacks [6] against DNS infrastructure enable subsequent   targetted attacks on specific application layer sources or   destinations.  The general method appears to be to attack DNS   infrastructure, in these cases infrastructure that is towards the top   of the DNS naming hierarchy and "far" from the presumed targets, in   order to be able to fake DNS responses to a PKI, thereby acquiring   TLS server certificates so as to subsequently attack TLS connections   from clients to services (with clients directed to an attacker-owned   server via additional fake DNS responses).   Attackers in these cases seem well resourced and patient - with   "practice" runs over months and with attack durations being   infrequent and short (e.g. 1 hour) before the attacker withdraws.   These are sophisticated multi-protocol attacks, where weaknesses   related to deployment of one protocol (DNS) bootstrap attacks on   another protocol (e.g.  IMAP/TLS), via abuse of a 3rd protocol   (ACME), partly in order to capture user IMAP login credentials, so as   to be able to harvest message store content from a real message   store.   The fact that many mail clients regularly poll their message store   means that a 1-hour attack is quite likely to harvest many cleartext   passwords or crackable password hashes.  The real IMAP server in such   a case just sees fewer connections during the "live" attack, and some   additional connections later.  Even heavy email users in such cases   that might notice a slight gap in email arrivals, would likely   attribute that to some network or service outage.   In many of these cases the paucity of DNSSEC-signed zones (about 1%   of existing zones) and the fact that many resolvers do not enforceFarrell                  Expires January 7, 2020                [Page 7]

Internet-Draft                     etm                         July 2019   DNSSEC validation (e.g., in some mobile operating systems) assisted   the attackers.   It is also notable that some of the personnel dealing with these   attacks against infrastructure entites are authors of RFCs and   Internet-drafts.  That we haven't provided protocol tools that better   protect against these kinds of attack ought hit "close to home" for   the IETF.   In terms of the overall argument being made here, the PKI and DNS   interactions, and the last step in the "live" attack all involve   interaction with a deliberately adversarial application.  Later, use   of acquired login credentials to harvest message store content   involves an adversarial client application.  It all cases, a TLS   implementation's PKI and TLS protocol code will see the fake   endpoints as protocol-valid, even if, in the real world, they are   clearly fake.  This appears to be a good argument that our current   threat model is lacking in some respect(s), even as applied to our   currently most important security protocol (TLS).2.11.  BGP hijacking   There is a clear history of BGP hijacking [bgphijack] being used to   ensure endpoints connect to adversarial applications.  As in the   previous example, such hijacks can be used to trick a PKI into   issuing a certificate for a fake entity.  Indeed one study   [hijackdet] used the emergence of new web server TLS key pairs during   the event, (detected via Internet-wide scans), as a distinguisher   between one form of deliberate BGP hijacking and indadvertent route   leaks.3.  Inadvertent adversarial behaviours   Not all adversarial behaviour by applications is deliberate, some is   likely due to various levels of carelessness (some quite   understandable, others not) and/or due to erroneous assumptions about   the environments in which those applications (now) run.   We very briefly list some such cases:   o  Application abuse for command and control, for example, use of IRC      or apache logs for malware command and control [7]   o  Carelessly leaky buckets [8], for example, lots of Amazon S3 leaks      showing that careless admins can too easily cause application      server data to become available to adversaries   o  Virtualisation exposing secrets, for example, Meltdown and Spectre      [9] and similar side-channelsFarrell                  Expires January 7, 2020                [Page 8]

Internet-Draft                     etm                         July 2019   o  Compromised badly-maintained web sites, that for example, have led      to massive online databases of passwords [10]   o  Supply-chain attacks, for example, the Target attack [11] or      malware within pre-installed applications on Android phones.      [bloatware]   o  Breaches of major service providers, that many of us might have      assumed would be sufficiently capable to be the best large-scale      "Identity providers", for example:      *  3 billion accounts: yahoo [12]      *  "up to 600M" account passwords stored in clear: facebook [13]      *  many millions at risk: telcos selling location data [14]      *  50 million accounts: facebook [15]      *  14 million accounts: verizon [16]      *  "hundreds of thousands" of accounts: google [17]      *  unknown numbers, some email content exposed: microsoft [18]   o  Breaches of smaller service providers: Too many to enumerate,      sadly4.  Possible directions for an expanded threat model   As we believe useful conclusions in this space require community   consensus, we won't offer definitive descriptions of an expanded   threat model but we will call out some potential directions that   could be explored as one follow-up to the DEDR workshop and   thereafter, if there is interest in this topic.   Before doing so, it is worth calling out one of the justifications   for theRFC 3553 definition of the Internet threat model which is   that going beyond an assumption that protocol endpoints have not been   compromised rapidly introduces complexity into the analysis.  We do   have plenty of experience that when security and privacy solutions   add too much complexity and/or are seen to add risks without   benefits, those tend not to be deployed.  One of the risks in   expanding our threat model that we need to recognise is that the end   result could be too complex, might not be applied during protocol   design, or worse, could lead to flawed risk analyses.  One of the   constraints on work on an expanded threat model is therefore that theFarrell                  Expires January 7, 2020                [Page 9]

Internet-Draft                     etm                         July 2019   result has to remain usable by protocol designers who are not   security or privacy experts.4.1.  Develop a BCP for privacy considerations   It may be time for the IETF to develop a BCP for privacy   considerations, possibly starting from [RFC6973].4.2.  Consider the user perspective   [I-D.nottingham-for-the-users] argues that, in relevant cases where   there are conflicting requirements, the "IETF considers end users as   its highest priority concern."  Doing so seems consistent with the   expanded threat model being argued for here, so may indicate that a   BCP in that space could also be useful.4.3.  Consider ABuse-cases as well as use-cases   Protocol developers and those implementing and deploying Internet   technologies are typically most interested in a few specific use-   cases for which they need solutions.  Expanding our threat model to   include adversarial application behaviours [abusecases] seems likely   to call for significant attention to be paid to potential abuses of   whatever new or re-purposed technology is being considered.4.4.  Re-consider protocol design "lore"   It could be that this discussion demonstrates that it is timely to   reconsider some protocol design "lore" as for example is done in   [I-D.iab-protocol-maintenance].  More specifically, protocol   extensibility mechanisms may inadvertently create vectors for abuse-   cases, given that designers cannot fully analyse their impact at the   time a new protocol is defined or standardised.  One might conclude   that a lack of extensibility could be a virtue for some new   protocols, in contrast to earlier assumptions.  As pointed out by one   commenter though, people can find ways to extend things regardless,   if they feel the need.4.5.  Isolation   Sophisticated users can sometimes deal with adversarial behaviours in   applications by using different instances of those applications, for   example, differently configured web browsers for use in different   contexts.  Applications (including web browsers) and operating   systems are also building in isolation via use of different processes   or sandboxing.  Protocol artefacts that relate to uses of such   isolation mechanisms might be worth considering.  To an extent, the   IETF has in practice already recognised some of these issues as beingFarrell                  Expires January 7, 2020               [Page 10]

Internet-Draft                     etm                         July 2019   in-scope, e.g.  when considering the linkability issues with   mechanisms such as TLS session tickets, or QUIC connection   identifiers.4.6.  Transparency   Certificate transparency (CT) [RFC6962] has been an effective   countermeasure for X.509 certificate mis-issuance, which used be a   known application layer misbehaviour in the public web PKI.  CT can   also help with post-facto detection of some infrastructure attacks   where BGP or DNS weakenesses have been leveraged so that some   certification authority is tricked into issuing a certificate for the   wrong entity.   While the context in which CT operates is very constrained   (essentially to the public CAs trusted by web browsers), similar   approaches could perhaps be useful for other protocols or   technologies.   In addition, legislative requirements such as those imposed by the   GDPR for subject access to data [19] could lead to a desire to handle   internal data structures and databases in ways that are reminiscent   of CT, though clearly with significant authorisation being required   and without the append-only nature of a CT log.4.7.  Minimise   As recommended in [RFC6973] data minimisation and additional   encryption are likely to be helpful - if applications don't ever see   data, or a cleartext form of data, then they should have a harder   time misbehaving.  Similarly, not adding new long-term identifiers,   and not exposing existing ones, would seem helpful.4.8.  Same-Origin Policy   The Same-Origin Policy (SOP) [RFC6454] perhaps already provides an   example of how going beyond theRFC 3552 threat model can be useful.   Arguably, the existence of the SOP demonstrates that at least web   browsers already consider the 3552 model as being too limited.   (Clearly, differentiating between same and not-same origins   implicitly assumes that some origins are not as trustworthy as   others.)4.9.  Greasing   The TLS protocol [RFC8446] now supports the use of GREASE   [I-D.ietf-tls-grease] as a way to mitigate on-path ossification.   While this technique is not likely to prevent any deliberateFarrell                  Expires January 7, 2020               [Page 11]

Internet-Draft                     etm                         July 2019   misbehaviours, it may provide a proof-of-concept that network   protocol mechanisms can have impact in this space, if we spend the   time to try analyse the incentives of the various parties.4.10.  Generalise OAuth Threat Model   The OAuth threat model [RFC6819] provides an extensive list of   threats and security considerations for those implementing and   deploying OAuth version 2.0 [RFC6749].  That document is perhaps too   detailed to serve as useful generic guidance but does go beyond the   Internet threat model fromRFC3552, for example it says:     two of the three parties involved in the OAuth protocol may     collude to mount an attack against the 3rd party.  For example,     the client and authorization server may be under control of an     attacker and collude to trick a user to gain access to resources.   It could be useful to attempt to derive a more abstract threat model   from that RFC that considers threats in more generic multi-party   contexts.4.11.  One (or more) endpoint may be compromised   The quote from OAuth above also has another aspect - it considers the   effect of compromised endpoints on those that are not compromised.   It may therefore be interesting to consider the consequeneces that   would follow from this OLD/NEW change toRFC3552   OLD: In general, we assume that the end-systems engaging in a   protocol exchange have not themselves been compromised.   NEW:   In general, we assume that one of the protocol engines engaging in a   protocol exchange has not been compromised at the run-time of the   exchange.4.12.  Look again at how well we're securing infrastructure   Some attacks (e.g. against DNS or routing infrastructure) appear to   benefit from current infrastructure mechanisms not being deployed,   e.g.  DNSSEC, RPKI.  In the case of DNSSEC, deployment is still   minimal despite much time having elapsed.  This suggests a number of   different possible avenues for investigation:   o  For any protocol dependent on infrastructure like DNS or BGP, we      ought analysse potential outcomes in the event the relevant      infrastructure has been compromisedFarrell                  Expires January 7, 2020               [Page 12]

Internet-Draft                     etm                         July 2019   o  Protocol designers perhaps ought consider post-facto detection      compromise mechanisms in the event that it is infeasible to      mitigate attacks on infrastructure that is not under local control   o  Despite the sunk costs, it may be worth re-considering      infrastructure security mechanisms that have not been deployed,      and hence are ineffective.4.13.  Consider recovery from attack as part of protocol design   Recent work on multiparty messaging security primitives   [I-D.ietf-mls-architecture] considers "post-compromise security" as   an inherent part of the design of that protocol.  Perhaps protocol   designers ought generally consider recovery from attack during   protocol design - we do know that all widely used protocols will at   sometime be subject to successful attack, whether that is due to   deployment or implementation error, or, as is less common, due to   protocol design flaws.4.14.  Don't think in terms of hosts   More and more, protocol endpoints are not being executed on what used   be understood as a host system.  The web and Javascript model clearly   differs from traditional host models, but so do most server-side   deployments these days, thanks to virtualisation.   As yes unpublished work on this topic within the IAB stackevo [20]   programme, appears to posit the same kind of thesis.  In the stackevo   case, that work would presumably lead to some new definition of   protocol endpoint, but (consensus on) such a definition may not be   needed for an expanded threat model.  For this work, it may be   sufficient to note that protocol endpoints can no longer be   considered to be executing on a traditional host, to assume (at   protocol design time) that all endpoints will be run in a virtualised   environment where co-tenants and (sometimes) hypervisors are   adversaries, and to then call for analysis of such scenarios.5.  Conclusions   At this stage we don't think it approriate to claim that any strong   conclusion can be reached based on the above.  We do however, claim   that the is a topic that could be worth discussion as part of the   follow-up to at the DEDR workshop and more generally within the IETF.Farrell                  Expires January 7, 2020               [Page 13]

Internet-Draft                     etm                         July 20196.  Security Considerations   This draft is all about security, and privacy.   Encryption is one of the most effective tools in countering network   based attackers and will also have a role in protecting against   adversarial applications.  However, today many existing tools for   countering adversarial applications assume they can inspect network   traffic to or from potentially adversarial applications.  These facts   of course cause tensions (e.g. see [RFC8404]).  Expanding our threat   model could possibly help reduce some of those tensions, if it leads   to the development of protocols that make exploitation harder or more   transparent for adversarial applications.7.  IANA Considerations   There are no IANA considerations.8.  Acknowledgements   With no implication that they agree with some or all of the above,   thanks to Jari Arkko, Carsten Bormann, Christian Huitema and Daniel   Kahn Gillmor for comments on an earlier version of the text.   Thanks to Jari Arkko, Ted Hardie and Brian Trammell for discussions   on this topic after they (but not the author) had attended the DEDR   workshop.9.  References9.1.  Informative References   [abusecases]              McDermott, J. and C. Fox, "Using abuse case models for              security requirements analysis", IEEE Annual Computer              Security Applications Conference (ACSAC'99) 1999, 1999,              <https://www.acsac.org/1999/papers/wed-b-1030-john.pdf>.   [attitude]              Chanchary, F. and S. Chiasson, "User Perceptions of              Sharing, Advertising, and Tracking", Symposium on Usable              Privacy and Security (SOUPS) 2015, 2015,              <https://www.usenix.org/conference/soups2015/proceedings/presentation/chanchary>.Farrell                  Expires January 7, 2020               [Page 14]

Internet-Draft                     etm                         July 2019   [bgphijack]              Sermpezis, P., Kotronis, V., Dainotti, A., and X.              Dimitropoulos, "A survey among network operators on BGP              prefix hijacking",  ACM SIGCOMM Computer Communication              Review 48, no. 1 (2018): 64-69., 2018,              <https://arxiv.org/pdf/1801.02918.pdf>.   [bloatware]              Gamba, G., Rashed, M., Razaghpanah, A., Tapiado, J., and              N. Vallina-Rodriguez, "An Analysis of Pre-installed              Android Software",  arXiv preprint arXiv:1905.02713              (2019)., 2019, <https://arxiv.org/pdf/1905.02713.pdf>.   [cambridge]              Isaak, J. and M. Hanna, "User Data Privacy: Facebook,              Cambridge Analytica, and Privacy Protection",              Computer 51.8 (2018): 56-59, 2018,              <https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8436400>.   [curated]  Hammad, M., Garcia, J., and S. MaleK, "A large-scale              empirical study on the effects of code obfuscations on              Android apps and anti-malware products", ACM International              Conference on Software Engineering 2018, 2018,              <https://www.ics.uci.edu/~seal/publications/2018ICSE_Hammad.pdf>.   [hijackdet]              Schlamp, J., Holz, R., Gasser, O., Korste, A., Jacquemart,              Q., Carle, G., and E. Biersack, "Investigating the nature              of routing anomalies: Closing in on subprefix hijacking              attacks",  International Workshop on Traffic Monitoring              and Analysis, pp. 173-187. Springer, Cham, 2015., 2015,              <https://www.net.in.tum.de/fileadmin/bibtex/publications/papers/schlamp_TMA_1_2015.pdf>.   [I-D.arkko-arch-internet-threat-model]              Arkko, J., "Changes in the Internet Threat Model",draft-arkko-arch-internet-threat-model-00 (work in progress),              April 2019.   [I-D.iab-protocol-maintenance]              Thomson, M., "The Harmful Consequences of the Robustness              Principle",draft-iab-protocol-maintenance-03 (work in              progress), May 2019.Farrell                  Expires January 7, 2020               [Page 15]

Internet-Draft                     etm                         July 2019   [I-D.ietf-mls-architecture]              Omara, E., Beurdouche, B., Rescorla, E., Inguva, S., Kwon,              A., and A. Duric, "The Messaging Layer Security (MLS)              Architecture",draft-ietf-mls-architecture-02 (work in              progress), March 2019.   [I-D.ietf-tls-grease]              Benjamin, D., "Applying GREASE to TLS Extensibility",draft-ietf-tls-grease-02 (work in progress), January 2019.   [I-D.nottingham-for-the-users]              Nottingham, M., "The Internet is for End Users",draft-nottingham-for-the-users-08 (work in progress), June 2019.   [mailbug]  Englehardt, S., Han, J., and A. Narayanan, "I never signed              up for this! Privacy implications of email tracking",              Proceedings on Privacy Enhancing Technologies 2018.1              (2018): 109-126., 2018,              <https://www.degruyter.com/downloadpdf/j/popets.2018.2018.issue-1/popets-2018-0006/popets-2018-0006.pdf>.   [RFC1984]  IAB and IESG, "IAB and IESG Statement on Cryptographic              Technology and the Internet",BCP 200,RFC 1984,              DOI 10.17487/RFC1984, August 1996,              <https://www.rfc-editor.org/info/rfc1984>.   [RFC2804]  IAB and IESG, "IETF Policy on Wiretapping",RFC 2804,              DOI 10.17487/RFC2804, May 2000,              <https://www.rfc-editor.org/info/rfc2804>.   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC              Text on Security Considerations",BCP 72,RFC 3552,              DOI 10.17487/RFC3552, July 2003,              <https://www.rfc-editor.org/info/rfc3552>.   [RFC6454]  Barth, A., "The Web Origin Concept",RFC 6454,              DOI 10.17487/RFC6454, December 2011,              <https://www.rfc-editor.org/info/rfc6454>.   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",RFC 6749, DOI 10.17487/RFC6749, October 2012,              <https://www.rfc-editor.org/info/rfc6749>.   [RFC6819]  Lodderstedt, T., Ed., McGloin, M., and P. Hunt, "OAuth 2.0              Threat Model and Security Considerations",RFC 6819,              DOI 10.17487/RFC6819, January 2013,              <https://www.rfc-editor.org/info/rfc6819>.Farrell                  Expires January 7, 2020               [Page 16]

Internet-Draft                     etm                         July 2019   [RFC6962]  Laurie, B., Langley, A., and E. Kasper, "Certificate              Transparency",RFC 6962, DOI 10.17487/RFC6962, June 2013,              <https://www.rfc-editor.org/info/rfc6962>.   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,              Morris, J., Hansen, M., and R. Smith, "Privacy              Considerations for Internet Protocols",RFC 6973,              DOI 10.17487/RFC6973, July 2013,              <https://www.rfc-editor.org/info/rfc6973>.   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an              Attack",BCP 188,RFC 7258, DOI 10.17487/RFC7258, May              2014, <https://www.rfc-editor.org/info/rfc7258>.   [RFC8240]  Tschofenig, H. and S. Farrell, "Report from the Internet              of Things Software Update (IoTSU) Workshop 2016",RFC 8240, DOI 10.17487/RFC8240, September 2017,              <https://www.rfc-editor.org/info/rfc8240>.   [RFC8404]  Moriarty, K., Ed. and A. Morton, Ed., "Effects of              Pervasive Encryption on Operators",RFC 8404,              DOI 10.17487/RFC8404, July 2018,              <https://www.rfc-editor.org/info/rfc8404>.   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol              Version 1.3",RFC 8446, DOI 10.17487/RFC8446, August 2018,              <https://www.rfc-editor.org/info/rfc8446>.   [smarttv]  Malkin, N., Bernd, J., Johnson, M., and S. Egelman, ""What              Can't Data Be Used For?" Privacy Expectations about Smart              TVs in the U.S.", European Workshop on Usable Security              (Euro USEC) 2018, 2018, <https://www.ndss-symposium.org/wp-content/uploads/2018/06/eurousec2018_16_Malkin_paper.pdf>.   [sybil]    Viswanath, B., Post, A., Gummadi, K., and A. Mislove, "An              analysis of social network-based sybil defenses", ACM              SIGCOMM Computer Communication Review 41(4), 363-374.              2011, 2011,              <https://conferences.sigcomm.org/sigcomm/2010/papers/sigcomm/p363.pdf>.   [toys]     Chu, G., Apthorpe, N., and N. Feamster, "Security and              Privacy Analyses of Internet of Things Childrens' Toys",              IEEE Internet of Things Journal 6.1 (2019): 978-985.,              2019, <https://arxiv.org/pdf/1805.02751.pdf>.Farrell                  Expires January 7, 2020               [Page 17]

Internet-Draft                     etm                         July 2019   [tracking]              Ermakova, T., Fabian, B., Bender, B., and K. Klimek, "Web              Tracking-A Literature Review on the State of Research",               Proceedings of the 51st Hawaii International Conference              on System Sciences, 2018,              <https://scholarspace.manoa.hawaii.edu/bitstream/10125/50485/paper0598.pdf>.   [troll]    Stewart, L., Arif, A., and K. Starbird, "Examining trolls              and polarization with a retweet network", ACM Workshop on              Misinformation and Misbehavior Mining on the Web 2018,              2018, <https://faculty.washington.edu/kstarbi/examining-trolls-polarization.pdf>.   [unread]   Obar, J. and A. Oeldorf-Hirsch, "The biggest lie on the              internet: Ignoring the privacy policies and terms of              service policies of social networking services",              Information, Communication and Society (2018): 1-20, 2018,              <https://doi.org/10.1080/1369118X.2018.1486870>.   [vpns]     Khan, M., DeBlasio, J., Voelker, G., Snoeren, A., Kanich,              C., and N. Vallina-Rodrigue, "An empirical analysis of the              commercial VPN ecosystem", ACM Internet Measurement              Conference 2018 (pp. 443-456), 2018,              <https://eprints.networks.imdea.org/1886/1/imc18-final198.pdf>.9.2.  URIs   [1]https://datatracker.ietf.org/doc/rfc6973/referencedby/   [2]https://datatracker.ietf.org/doc/rfc7258/referencedby/   [3]https://www.iab.org/activities/workshops/dedr-workshop/   [4]https://www.nytimes.com/2018/10/20/us/politics/saudi-image-campaign-twitter.html   [5]https://www.welivesecurity.com/2013/11/22/lg-admits-that-its-smart-tvs-have-been-watching-users-and-transmitting-data-without-       consent/   [6]https://krebsonsecurity.com/2019/02/a-deep-dive-on-the-recent-widespread-dns-hijacking-attacks/   [7]https://security.stackexchange.com/questions/100577/creating-botnet-cc-server-what-architecture-should-i-use-irc-httpFarrell                  Expires January 7, 2020               [Page 18]

Internet-Draft                     etm                         July 2019   [8]https://businessinsights.bitdefender.com/worst-amazon-breaches   [9]https://www.us-cert.gov/ncas/alerts/TA18-004A   [10]https://haveibeenpwned.com/Passwords   [11]https://www.zdnet.com/article/how-hackers-stole-millions-of-credit-card-records-from-target/   [12]https://www.wired.com/story/yahoo-breach-three-billion-accounts/   [13]https://www.pcmag.com/news/367319/facebook-stored-up-to-600m-user-passwords-in-plain-text   [14]https://www.zdnet.com/article/us-telcos-caught-selling-your-location-data-again-senator-demands-new-laws/   [15]https://www.cnet.com/news/facebook-breach-affected-50-million-people/   [16]https://www.zdnet.com/article/millions-verizon-customer-records-israeli-data/   [17]https://www.wsj.com/articles/google-exposed-user-data-feared-repercussions-of-disclosing-to-public-1539017194   [18]https://motherboard.vice.com/en_us/article/ywyz3x/hackers-could-read-your-hotmail-msn-outlook-microsoft-customer-support   [19]https://gdpr-info.eu/art-15-gdpr/   [20]https://github.com/stackevo/endpoint-draft/blob/master/draft-trammell-whats-an-endpoint.mdAppendix A.  Change Log   This isn't gonna end up as an RFC, but may as well be tidy...A.1.  Changes from -02 to -03   o  Integrated some changes based on discussion with Ted, Jari and      Brian.A.2.  Changes from -01 to -02   o  Oops - got an RFC number wrong in referenceFarrell                  Expires January 7, 2020               [Page 19]

Internet-Draft                     etm                         July 2019A.3.  Changes from -00 to -01   o  Made a bunch more edits and added more references   o  I had lots of typos (as always:-)   o  cabo: PR#1 fixed more typos and noted extensbility dangerAuthor's Address   Stephen Farrell   Trinity College Dublin   Email: stephen.farrell@cs.tcd.ieFarrell                  Expires January 7, 2020               [Page 20]
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