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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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