Spam control modules

Spam -- whether in a post, comment or through a contact form -- has become a troublesome fact of life for any site administrator. Fortunately, a number of modules help stem the tide of spam, either by real-time filtering, challenge-response interaction, or a combination of the two.

One common method of preventing automated spam postings is to employ a module that injects a CAPTCHA into common Drupal forms, like the user registration, comment and contact pages. If the CAPTCHA, a visual or auditory challenge, can be completed with the correct response, the user is assumed to be human and not an automated spam-posting process. See the CAPTCHA and ReCAPTCHA documentation or project pages for two modules that provide this functionality.

Mollom is a popular spam filtering service that analyzes content in real-time for spam-like characteristics. Content identified as spam is blocked, while clean content is processed normally. If Mollom is unsure whether the content is spam, it directs your site to require a successful CAPTCHA completion before the post is accepted. Akismet is a similar, older and less popular, external service for spam filtering. For filtering without any external services, the Spam module integrates a Bayesian filter along with some other filtering methods.

Although the following modules have additional documentation, other spam control modules may exist in the contributions repository. Reviewing the module usage statistics may be helpful when selecting a spam control module.