I-D ACTION:draft-tschofenig-sipping-captcha-00.txt

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	Title		: Completely Automated Public Turing Test to Tell Computers and Humans Apart (CAPTCHA) based Robot Challenges for the Session Initiation Protocol (SIP)
	Author(s)	: H. Tschofenig, E. Leppanen
	Filename	: draft-tschofenig-sipping-captcha-00.txt
	Pages		: 21
	Date		: 2007-7-5

   Spam over Internet Telephony (SPIT) is one of the foreseen future
   forms of spamming that SIP networks may have to handle.  SPIT also
   has more impact on users than email spam since it is more intrusive.
   Email as a store-and-forward communication mechanism allows for
   several filtering mechanisms to be applied to the full content before
   being presented to the user.  Session Initiation Protocol (SIP)

   interaction is, in contrast, real-time communication and therefore
   does not provide much information prior to the transmission of the
   content, making it both harder to filter and more annoying to users.
   The responsibility for filtering, blocking calls, or taking any other
   preventive action can belong to different elements in the call flow
   and may depend on various factors.

   This document concentrates on "Completely Automated Public Turing
   Test to Tell Computers and Humans Apart" (CAPTCHA) tests, which
   require human interaction.  The document proposes an approach how to
   apply those challenges to SIP communication for handling the SPIT
   problem.

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