Honeypot

Honeypot uses both the honeypot and timestamp methods of deterring spam bots from completing forms on your Drupal site.

A lot of people use form spam prevention methods like CAPTCHAs or math problems that require extra user interaction, and cause some users to have trouble filling out online forms. For most small sites, something as complicated as a CAPTCHA is not really necessary anyways. Therefore, I wrote the Honeypot module, which adds invisible form elements to selected forms, and checks to make sure the form elements are not filled out by spam bots.

This spam detection method is sophisticated enough to thwart non-targeted spam bot attacks (the most frequent spam attacks for smaller websites like personal sites and blogs), and has successfully reduced the amount of spam posts and user accounts on hundreds of Drupal websites, all while keeping the user experience of completing online forms as simple as possible.