freecap - PHP CAPTCHA script

freeCap can be used to prevent spam on any form; guestbook, comment area, signups, shopping carts - any area of your website where you fear the evil spammers may target.

freeCap boasts a host of features, not only does it offer strong character obfuscation, using random distortion of text and multiple backgrounds, but it also focuses on the security of the implementation. A lot of CAPTCHAs are secure against OCR attacks, but fail to account for other attacks, such as session re-use and cross-vhost file inclusion on shared servers.

freeCap can output in three different image types, uses a custom GD font for each character, has brute force protection, it's open source GPL and is totally self-contained - no need for SQL databases, PEAR, or anything beyond PHP and GD!
I hope you like it

Requirements:
PHP 4.01+
GDlib any version (for gif support, any except 1.06)
Runs on both linux and windows platforms.

freeCap CAPTCHA Version 1.4.1
Features:
as version 1.3, plus:
-optional sha1 / md5 / crc32 hash in server session
-3 different randomly generated background types: grid, squiggles, image blocks (or blank) - see the demo!
-multiple font/colour support
-htaccess protected dictionary, fonts and backgrounds
-shared server security further enhanced
-user definable text fading
-automatic random number seeding for older PHP versions