What is CAPTCHA?

CAPTCHA stands for *C*ompletely *A*utomated *P*ublic *T*uring test to tell *C*omputers and *H*umans *A*part. Basically it means those pictures with wavy letters that you have to type in before being allowed to sign up for a mailing list or other service. They are an attempt to prevent “spamming” or automatic signups by programs. Apparently there are some audio versions as well. 
 
 http://www.captcha.net/ 	 http://en.wikipedia.org/wiki/Captcha 	 PHP CAPTCHA Class 	 http://www.codeproject.com/aspnet/CaptchaImage.asp 
 
 reCAPTCHA is a very intriguing project that uses CAPTCHA authentication to help correct OCRA software and digitize books for the internet archive. Fiat Lux! 
 
 Techniques and Arguments against CAPTCHA 
 
 http://www.cs.sfu.ca/~mori/research/gimpy/ 	 http://sam.zoy.org/pwntcha/ 	 Escape from CAPTCHA Presentation 	 Inaccessibility of Visually Oriented Anti-Robot Tests