A Survey of Worldwide Censorship Techniques
draft-hall-censorship-tech-07

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Network Working Group                                            J. Hall
Internet-Draft                                                       CDT
Intended status: Informational                                  M. Aaron
Expires: September 12, 2019                                   CU Boulder
                                                                S. Adams
                                                                     CDT
                                                                B. Jones
                                                             N. Feamster
                                                               Princeton
                                                          March 11, 2019

              A Survey of Worldwide Censorship Techniques
                     draft-hall-censorship-tech-07

Abstract

   This document describes the technical mechanisms used by censorship
   regimes around the world to block or impair Internet traffic.  It
   aims to make designers, implementers, and users of Internet protocols
   aware of the properties being exploited and mechanisms used to censor
   end-user access to information.  This document makes no suggestions
   on individual protocol considerations, and is purely informational,
   intended to be a reference.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 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 at https://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 September 12, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Hall, et al.           Expires September 12, 2019               [Page 1]
Internet-Draft         draft-hall-censorship-tech             March 2019

   This document is subject to BCP 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Technical Prescription  . . . . . . . . . . . . . . . . . . .   3
   3.  Technical Identification  . . . . . . . . . . . . . . . . . .   4
     3.1.  Points of Control . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Application Layer . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  HTTP Request Header Identification  . . . . . . . . .   5
       3.2.2.  HTTP Response Header Identification . . . . . . . . .   6
       3.2.3.  Instrumenting Content Providers . . . . . . . . . . .   7
       3.2.4.  Deep Packet Inspection (DPI) Identification . . . . .   8
     3.3.  Transport Layer . . . . . . . . . . . . . . . . . . . . .  10
       3.3.1.  Shallow Packet Inspection and TCP/IP Header
               Identification  . . . . . . . . . . . . . . . . . . .  10
       3.3.2.  Protocol Identification . . . . . . . . . . . . . . .  11
   4.  Technical Interference  . . . . . . . . . . . . . . . . . . .  12
     4.1.  Application Layer . . . . . . . . . . . . . . . . . . . .  12
       4.1.1.  DNS Interference  . . . . . . . . . . . . . . . . . .  12
     4.2.  Transport Layer . . . . . . . . . . . . . . . . . . . . .  14
       4.2.1.  Performance Degradation . . . . . . . . . . . . . . .  14
       4.2.2.  Packet Dropping . . . . . . . . . . . . . . . . . . .  15
       4.2.3.  RST Packet Injection  . . . . . . . . . . . . . . . .  15
     4.3.  Multi-layer and Non-layer . . . . . . . . . . . . . . . .  16
       4.3.1.  Distributed Denial of Service (DDoS)  . . . . . . . .  16
       4.3.2.  Network Disconnection or Adversarial Route
               Announcement  . . . . . . . . . . . . . . . . . . . .  17
   5.  Non-Technical Prescription  . . . . . . . . . . . . . . . . .  18
   6.  Non-Technical Interference  . . . . . . . . . . . . . . . . .  18
     6.1.  Self-Censorship . . . . . . . . . . . . . . . . . . . . .  18
     6.2.  Domain Name Reallocation  . . . . . . . . . . . . . . . .  19
     6.3.  Server Takedown . . . . . . . . . . . . . . . . . . . . .  19
     6.4.  Notice and Takedown . . . . . . . . . . . . . . . . . . .  19