3 plugins tagged with spambots
NURCaptcha inserts a reCAPTCHA on the Register Form of your site to protect it against spambots.
Block SPAM without any type of CAPTCHA - plugin add "HoneyTrap" (and a few other tricks) for comment form to block SPAMbots.
This plugin validates email in realtime using live connections and aggregated data, by leveraging the ThreatPoint email verification API service.