PRyC WP: AntiSPAM (without CAPTCHA) Wordpress Plugin - Rating, Reviews, Demo & Download
Plugin Description
Block SPAM without any type of CAPTCHA – plugin add “HoneyTrap” (and a few other tricks) for comment form to block SPAMbots.
Plugin add “HoneyTrap” for comment form to block SPAMbots. Most od SPAM bot fills all comment fields (especially marked as required). plugin also use a few other tricks to eliminate SPAM from spambots.
Work fine for all my and my client site 🙂
Plug will not stop people writing comments – to block this type of spam additionally install eg. Akismet or Antispam Bee.