Spam Free WordPress Features
- Automatically blocks 100% of automated comment spam
- Local manual spam and ban policy set with local IP address blocklist
- Global manual spam and ban policy set with remote IP address blocklist
- Significantly reduces database load compared to other spam plugins
- Zero false positives
- Option to strip HTML from comments
- No CAPTCHA, cookies, or Javascript needed
- Saves time and money by eliminating the need to empty the comment spam folder
http://wordpress.org/extend/plugins/spam-free-wordpress/