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CAPTCHA: Telling Humans and Computers Apart Automatically - http://www.captcha.net/
Includes demonstrations, research papers, and news. |
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Wikipedia: CAPTCHA - http://en.wikipedia.org/wiki/CAPTCHA
Explains how captcha features can keep spammers from signing up for certain accounts online, such as email or weblogs. Explains how the system can be circumvented as well. |
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reCAPTCHA - http://recaptcha.net/
A captcha system that uses successful decodings to helps digitise books for online use. Background, and details on how to incorporate into a site. Source code in several languages, and plugins for popular blogging and CMS software. |
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Inaccessibility of CAPTCHA - http://www.w3.org/TR/turingtest/
A W3C Working Group Note explaining how CAPTCHAs can present a major obstacle to users who have limited vision or a learning disability such as dyslexia. This document examines a number of potential solutions and alternative systems. |
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Captcha Creator - http://www.captchacreator.com/
PHP Captcha Script that generates unique captcha images to stop automated submissions, highly customizable, easy to install and configure. |