Antibot (video)

The Antibot module is a SPAM prevent tool that does not require the end user to jump through any special hoops, such as completing a Captcha puzzle. It uses Javascript to detect if a user is likely a robot or human and then blocks robots without them even knowing they have been blocked. 

We've found it to be a relatively effective SPAM prevent tool, but it's not perfect. We definitely recommend giving it a try if you are having SPAM problems.