n3t Seznam Captcha
Simple text CAPTCHA with optional audio form, spelled in Czech language. It includes selectable theme and inline audio player with fallback download link.
This plugin wraps the seznam.cz Captcha API.
Additional protection by checking online spam databases and blacklists could be activated in the configuration. Currently StopForumSpam, SpamBusted, BotScout, SpamHaus, Sorbs, SpamCop and project HoneyPot are supported. There is also possibility to manually enter IP blacklist and/or whitelist.
Since version 1.2.0, there is option to disable visual CAPTCHA control, and use just additional protection.