This plugin allows you to implement Google Captcha (reCAPTCHA) into web forms.
An exceptionally powerful WordPress anti-spam plugin that eliminates comment spam, trackback spam, contact form spam & registration spam.
WordPress plugin to fight with more than 270 referrer spammers (like semalt, buttons-for-website and many more).
The best captcha alternative. Accessible, Mobile-friendly, and Retina-ready!
The plugin adds a No CAPTCHA reCAPTCHA tag in Contact Form 7, which can be used to include a No CAPTCHA reCAPTCHA anti-spam field.
Blocks referer spam from accessing your site and cleans up your Google Analytics in the process!
Block 250+ spam sites, such as semalt.com and 4webmasters.org! Keep your website safe and your Google Analytics statistics clean and accurate.
Comment spam prevention without moderation, captchas or questions
Unspam makes it harder for spammers to automatedly send spam to your blog by changing the names of the fields in the comment forms.
WP Spam IP is a simple and effective WordPress plugin that adds known Spam IP adresses to your Settings -> Discussion -> Comment Blacklist.
Best CAPTCHA solution, prevent spams, you can customized CAPTCHA challenge text and have people type Captcha it, better Captcha experience.
Check comment against the SpamBot Search Tool using the IP address, the email and the name of the poster as search criteria.
SiteBrains blocks spam posts using a completely configurable set of rules. Both interactively as the user types and on our servers upon submission.
A Clean, no hassle contact form plugin for WordPress, with advanced Spam bot protection that doesn't require Captcha.
Show spam statistics on your blog. (Now merged into SpamTask)
Tolero wordpress blog spam filter checks the submiter's bahavior. To operate properly it should have a physical access to the apache log file.