As I mention in, “Who is That on Your Website: Man or Machine,” a CAPTCHA is any automated process designed to differentiate between human and computerized posters.

CAPTCHA is especially useful for protecting your online forms, though it can also be helpful in keeping spammers from hijacking your blog, forum, or sign-up procedures.

Depending on your security needs, different kinds of CAPTCHA may be preferable.

Pre-built CAPTCHA

If there is a reason why someone would want to create multiple accounts on your page or frequently access some of your restricted information, you will want CAPTCHA which is harder to …