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Independent Submission                                      M. McFadden
Internet Draft                                 internet policy advisors
Intended status: Informational                            March 9, 2020
Expires: September 9, 2020

                        BCP72 - A Problem Statement

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   RFC3552/BCP72 describes an Internet Threat model that has been used
   in Internet protocol design. More than sixteen years have passed
   since RFC3552 was written and the structure and topology of the
   Internet has changed. With those changes comes a question: has the
   Internet Threat Model really changed? Or, is the model described in
   RFC3552 still largely accurate?  This draft attempts to describe an
   non-exhaustive list of changes in the current threat environment. It
   suggests that there are both qualitative and quantitative differences
   from the environment described in RFC3552 and is intended as input to
   the IAB program on the Internet threat model started in 2020.

Table of Contents

   1. Introduction...................................................2
   2. BCP72 Threat Model.............................................3
      2.1. BCP72 Passive Attacks.....................................3
      2.2. BCP72 Active Attacks......................................4
   3. Changes to the Attack Landscape................................4
      3.1. Quantifiable Changes......................................4
      3.2. Qualitative Changes.......................................5
      3.3. Data at Rest..............................................6
   4. Observations...................................................6
   5. Problem Statement..............................................7
   6. Security Considerations........................................8
   7. IANA Considerations............................................8
   8. References.....................................................8
      8.1. Normative References......................................8
      8.2. Informative References....................................8
   9. Acknowledgments................................................8

1. Introduction

   [RFC3552] describes an Internet threat model. According to that RFC
   the threat model "describes the capabilities that an attacker is
   assumed to be able to deploy against a resource. It should contain
   such information as the resources available to an attacker in terms
   of information, computing capability, and control of a system."

   In 2020, the IAB approved an IAB program on the Internet threat
   model. One of its goals was to explore how the world has changed in
   terms of threats experienced and how protocol endpoints are
   implemented and deployed.  During early discussions for that IAB
   program - called model-t - a natural question was raised: has the

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   Internet Threat Model really changed?  Or, is the model described in
   RFC3552 still largely accurate?

   The purpose of this draft is to examine the threat landscape of the
   contemporary Internet and answer those questions.  The draft might
   then be used as input into the IAB's model-t process for documenting
   why an update to BCP72 might be needed.

   Reconsideration of the guidelines for writing Security Considerations
   sections of RFCs is not in scope for this memo.

2. BCP72 Threat Model

   BCP72's threat model divides attacks based on the capabilities
   required to mount the attack.  In particular, it divides attacks into
   two groups: passive attacks where an attacker has only limited, or
   read-only, access to the network; and active attacks where the
   attacker has the resources available to write to the network.  BCP72
   is careful not to locate the attack.  The attacks can come from
   arbitrary endpoints. It's worth noting that dividing the threat model
   in this way also allows for the model to incorporate attacks that
   come from resources not at endpoints. In fact, an entire subsection
   of the BCP discusses on-path versus off-path attacks.

2.1. BCP72 Passive Attacks

   BCP72 details describes passive attacks as those in which an attacker
   "reads off the network but does not write them."  It then gives some
   specific examples including password sniffing, attacks on routing
   infrastructure, and unprotected wireless channels.

   The description in BCP72 tacitly assumes that the attacker is in
   control of a single resource.  For example, the first type of passive
   attack considered is one in which an attacker uses read-only access
   to packets to extract otherwise private information.  BCP72 discusses
   the problems encountered when packets are transported without some
   form of transport or application layer security.

   BCP72 also makes note of offline cryptographic attacks in which an
   attacker has made offline copies of packets that have read off the
   network. The attacker then mounts a cryptographic attack on those
   packets in order to extract confidential information from them

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2.2. BCP72 Active Attacks

   BCP72 says, "when an attack involves writing data to the network, we
   refer to this an an active attack."  In this case, the BCP discusses
   spoofing packets replay attacks, message insertion, deletion and
   insertion, man-in-the-middle, as well as a Denial of Service attack.

   In each of these cases the BCP suggests either mitigations or
   descriptions of what technologies could have been used to avoid the

3. Changes to the Attack Landscape

3.1. Quantifiable Changes

   In the period since 2003, one dramatic change is the number of
   attacks seen  Published studies {1} show orders of magnitude
   increases in the size of attacks. Recent studies show that the vast
   majority of attacks come from attackers using automated, distributed
   tools.  This makes a threat model that is built around the notion of
   a single attacker inapplicable in the current Internet.

   Studies also show that certain well-known ports [IANA-WKP] are the
   primary targets for this large jump in automated attacks.  Ports 445,
   22, 23, and 1433 make up 99% of the targets.

   The growth in the attacks on Telnet [RFC854] is a reflection of
   another development in the public Internet: the growth in numbers of
   constrained devices.  Endpoints that are not capable of supporting
   endpoint protection software, effective encryption, or proper
   authentication have proliferated on the public Internet.  That many
   of these devices do not have facilities for either self-protection or
   protecting against becoming a threat on their own has been documented
   in an IAB Workshop {IAB-IOT].

   Since 2003, there have been a variety of studies examining the growth
   in the number of devices connected to the Internet[2].  At the time
   of writing, one estimate is that the difference between the number of
   devices connected in 2003 and 2020 is in the region of 22 billion.
   The sheer quantity of devices means that the Internet's attack
   surface is significantly expanded.  Quantitative surveys also
   indicate that the greatest growth is in so-called enterprise IoT and
   household automation.  The security properties of these endpoints are
   potentially different from hosts that made up the majority of the
   Internet in 2003.

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   Another important quantitative change to the structure of the
   Internet is the consolidation of its infrastructure.  While BCP72 is
   certainly correct in its focus on the technologies and protocols that
   can be exploited by attackers, it is hard to ignore the fact that the
   threat landscape has been affected by the emergence of consolidation.
   One example of this would be commercial or governmental surveillance
   capabilities. In an environment where there are a small number of
   very large entities that control the fabric of connectivity and
   content, the threat landscape is affected by the fact that it may be
   easier to exert control and implement attacks on a small number of

3.2. Qualitative Changes

   The Internet in 2003 had a relatively small number of types of host.
   The client/server model of computing remained important at that time
   and endpoints were relatively homogeneous.

   The diversity of deployment is an important part of the contemporary
   Internet landscape.  Not only is there a measurable and huge increase
   in the number of endpoints (greatly increasing the attack surface),
   but there is rich diversity in the capacity, connectivity, purpose of
   those endpoints.  As a result, while the number of protocols may have
   not increased exponentially, the kinds of devices that can be sources
   or targets of exploits has increased significantly.

   The threat landscape is also affected by the balance between
   convenience versus protection from threats.  Today's landscape is
   affected by the conflict between protection from attackers and
   threats, and convenience.  Applications and services fight for market
   and mind share by being the easiest to adopt, install and use. Many
   users treat security and protection in the same way that they treat
   personal health - they ignore it until there is a serious problem and
   then expect the problem to be mitigated quickly.

   The class of attackers has changed as well. In 2003, advanced
   persistent attacks hadn't yet been given that name and the estimated
   monetary loss to attackers was estimated to the less than $1 billion
   ISD.  The emergence of scripted and other automated tools has changed
   the landscape dramatically.  In 2019, one estimate of losses due to
   network based attacks was in excess of $315 billion.  This is the
   direct result of the speed, financing and flexibility of those doing
   the attacking.

   It is true that, since BCP 72 was published there have been
   significant improvements to communications security.  This includes
   securing the transport layer through protocols such as TLS 1.3,

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   HTTP/2 and secure SMTP.  However, secure transport does not prevent
   rogue applications from executing attacks even when secure transport
   is in place.  Another example of this happens when VPNs themselves
   examine or exploit traffic rather than do what they are advertised to

3.3. Data at Rest

   The Internet Threat model in BCP72 primarily speaks to data being
   transmitted, transited or received over the network.  More recent
   approaches to providing services over the Internet involve
   intermediate nodes that may redirect, manipulate or store traffic.
   While technologies such as exchange points may be seen to simply part
   of the fabric between senders and receivers, the insertion of content
   networks, caches and traffic analyzers has become ubiquitous.

   These middle boxes play an important role in content provision,
   analysis and security in today's Internet. They were in limited use
   when BCP72 was published. The importance of these middleboxes is such
   that, when protocols are developed that effectively route around
   them, operators and content providers sometimes object.

   Any contemporary Internet threat model must go beyond the threats to
   traffic as it moves from Alice to Bob.  Beyond intermediaries, the
   more personal digital devices there are, the more difficult it is to
   control and protect them.  The threat model should also include
   attacks that take place when the data is at rest or being manipulated
   for operational reasons.

4. Observations

   If the IAB's Model T program finds that there have been both
   quantitative and qualitative changes to the Internet threat model,
   then perhaps it would be time to consider revising BCP72 to reflect
   those changes.  In this case the IAB should provide some initial
   assistance to the IETF on how to proceed with the revision.  Others
   have argued that the end-to-end architecture model of the Internet
   cannot be understood by just considering all of the protocol layers
   up to the application layer.[Arkko]

   In addition, BCP72's concentration on the communication channel fails
   to account for two of the central developments of the Internet in the
   last ten years: the rise of the application as the endpoint and the
   diversity of endpoints that are publicly connect.

   It might also be observed that there have already been limited
   attempts to reconsider BCP72's threat model.  As an example, the

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   Same-Origin Policy detailed in [RFC6454] shows how an application-
   layer protocol can protect itself against certain kinds of attacks
   based on the concept of origin (the determination and use of an
   origin URI).

   Finally, protection from phishing attacks in the presence of certain
   implementations of IDNA means that applications are implementing
   protections against certain types of attacks.  This is another
   example of how the application layer imposes controls on an otherwise
   secure communication channel.

   These are intended as only examples of how the landscape has changed.
   It seems clear that many more changes exist and need to be researched
   and documented.

5. Problem Statement

   BCP72 is an accurate reflection of the security threat landscape at
   the time which it was written.  While the work of the IAB program on
   the Internet threat model is essential, a revision to RFC3552 is in
   the remit of the IETF.

   BCP72 represents a too narrow view of the Internet's threat
   landscape. An update is needed to:

     .  Reflect the diversity of endpoint deployment on the Internet;

     .  Document the impact of application-based security on the more
        narrow communication channel model (possibly: consideration of
        data in use in addition to data in motion);

     .  Account for data at rest as part of the model as well as data
        in motion;

     .  Reflecting on the how the growth of the number of devices
        connected affects the attack surface for the Internet at large;

     .  Research by the IAB and others on how a new, contemporary
        threat model might be described and communicated to protocol
        designers and others; and,

     .  Make constructive suggestions for an approach (or, methodology)
        for the IETF to revise BCP72.

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6. Security Considerations

   This document is entirely about security on the Internet and is
   intended as input into the IAB's Model T work.

7. IANA Considerations

   The memo has no actions for IANA

8. References

8.1. Normative References

8.2. Informative References

   Informational references are to be added to a later version of this

9. Acknowledgments

   This document was prepared using 2-Word-v2.0.template.dot.

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Authors' Addresses

   Mark McFadden
   Internet policy advisors llc
   513 Elmside Blvd
   Madison WI 53704 US

   Phone: +1 608 504 7776
   Email: mark@internetpolicyadvisors.com

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