Bad Behavior is a PHP-based solution for blocking link spam and the robots which deliver it. It complements other link spam solutions by acting as a gatekeeper, preventing spammers from ever delivering their junk, and in many cases, from ever reading your site in the first place. This keeps your site’s load down, makes your site logs cleaner, and can help prevent denial of service conditions caused by spammers.
Bad Behavior also transcends other link spam solutions by working in a completely different, unique way. Instead of merely looking at the content of potential spam, Bad Behavior analyzes the delivery method as well as the software the spammer is using. In this way, Bad Behavior can stop spam attacks even when nobody has ever seen the particular spam before.
Bad Behavior works on, or can be adapted to, virtually any PHP-based Web software package. It is available natively for WordPress, MediaWiki, Drupal, ExpressionEngine, and LifeType, and people have successfully made it work with Movable Type, phpBB, and many other packages.