CAPTCHA

Captcha stands for "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a challenge-response test used in account creation or user log on to determine whether or not the user is human.

• CAPTCHA on Wikipedia: http://en.wikipedia.org/wiki/Captcha
• CAPTCHA Project: http://www.captcha.net/
• Free CAPTCHA Service: http://captchas.net
• CPAN query on CAPTCHA: http://search.cpan.org/search?query=captcha&mode=all
• Perl implementation: http://skriptke.ltn.net/hv/en.htm

TWiki related:

• VisualConfirmPlugin - CAPTCHA for TWiki registration
• CaptchaPlugin - VisualConfirmPlugin updated for Dakar

-- Contributors: PeterThoeny, WillNorris - 16 Jul 2006

http://yro.slashdot.org/yro/04/01/28/1344207.shtml describes an interesting realtime technique for circumventing CAPTCHA.

-- WillNorris - 18 Apr 2005

If you plan to code a CAPTCHA solution for TWiki, make sure it will destroy sessions afterwards... http://www.puremango.co.uk/cm_breaking_captcha_115.php

-- AlsterWassermann - 23 May 2005