CAPTCHA
- Carnegie Melon University.
The university originally coined the term 'CAPTCHA'. If you are looking for a quick fix solution or ready made plugins for WordPress, then their free Captcha service might be just what you're after. It includes both visual and audible challenges.
- W3C : WAI Captcha References
Whitepaper on Captcha accessibility, common barriers and alternative approaches to testing for programmatic agents.
- Google What's Up? CAPTCHA - CNET Article on a CAPTCHA developed by Google using rotated images and which is much simpler than obscurred character based approaches.
- Juicy Studio Article.
Accessibility of Captcha is an article considering accessibility issues and alternative approaches to testing for programmatic agents.
- freeCap 1.4 : PureMango
Very flexible and free to use graphical Captcha script in PHP. The script allows backgrounds, fonts and visual effects to be extensively customised.
- PWNtcha : Visit PWNtcha Website
Information on the breaking of graphical Captcha using image manipulation software to allow OCR. The site includes a list of commonly used Captcha scripts and provides a rating of their vulnerability to attack.
