The most advanced protection against sploggers and spam users registration, is fully WordPress,WordPress MU ,BuddyPress and bbPress 2.0 compatible
WangGuard Limited Registration Domain Add-On is an Add-on for WangGuard plugin. You can allow or disallow a list of domains.
WangGuard Blacklisted Words is an Add-on for WangGuard plugin. You can blacklist words.
WangGuard - MailPoet Connector is a plugin for connect WangGuard plugin with MailPoet.