AntiSpam Protect Web Form Captcha Plug-in for Drupal
supports English, German, French, Spanish, Russian localization.
Customize your CAPTCHA with desired colors and fonts. Chose among many image types.
Add reload button and audio support.
Bad Behavior is a set of PHP scripts which prevents spambots from accessing your site by analyzing their actual HTTP requests and comparing them to profiles from known spambots. It goes far beyond User-Agent and Referer, however.
The problem: Spammers run automated scripts which read everything on your web site, harvest email addresses, and if you have a blog, forum or wiki, will post spam...