Secure Telephone Identity Threat Model
draft-ietf-stir-threats-02

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Replaces draft-peterson-stir-threats
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Network Working Group                                        J. Peterson
Internet-Draft                                             NeuStar, Inc.
Intended status: Informational                         February 10, 2014
Expires: August 14, 2014

                 Secure Telephone Identity Threat Model
                     draft-ietf-stir-threats-02.txt

Abstract

   As the Internet and the telephone network have become increasingly
   interconnected and interdependent, attackers can impersonate or
   obscure calling party numbers when orchestrating bulk commercial
   calling schemes, hacking voicemail boxes or even circumventing multi-
   factor authentication systems trusted by banks.  This document
   analyzes threats in the resulting system, enumerating actors,
   reviewing the capabilities available to and used by attackers, and
   describing scenarios in which attacks are launched.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on August 14, 2014.

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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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Peterson                 Expires August 14, 2014                [Page 1]
Internet-Draft                STIR Threats                 February 2014

   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.

Table of Contents

   1.  Introduction and Scope  . . . . . . . . . . . . . . . . . . .   2
   2.  Actors  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Endpoints . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Intermediaries  . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Attackers . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Voicemail Hacking via Impersonation . . . . . . . . . . .   6
     3.2.  Unsolicited Commercial Calling from Impersonated Numbers    7
     3.3.  Telephony Denial-of-Service Attacks . . . . . . . . . . .   8
   4.  Attack Scenarios  . . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Solution-Specific Attacks . . . . . . . . . . . . . . . .  10
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction and Scope

   As is discussed in the STIR problem statement [2], the primary
   enabler of robocalling, vishing, swatting and related attacks is the
   capability to impersonate a calling party number.  The starkest
   examples of these attacks are cases where automated callees on the
   PSTN rely on the calling number as a security measure, for example to
   access a voicemail system.  Robocallers use impersonation as a means
   of obscuring identity; while robocallers can, in the ordinary PSTN,
   block (that is, withhold) their calling number from presentation,
   callees are less likely to pick up calls from blocked identities, and
   therefore appearing to calling from some number, any number, is
   preferable.  Robocallers however prefer not to call from a number
   that can trace back to the robocaller, and therefore they impersonate
   numbers that are not assigned to them.

   The scope of impersonation in this threat model pertains solely to
   the rendering of a calling telephone number to a callee (human user
   or automaton) at the time of call set-up.  The primary attack vector
   is therefore one where the attacker contrives for the calling
   telephone number in signaling to be a chosen number.  In this attack,
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