Tolero wordpress blog spam filter checks the submiter’s bahavior. To operate properly it should have a physical access to the apache log file.
Show spam statistics on your blog. (Now merged into SpamTask)
Anti-spam plugin – An advanced and free WP spam filter which protects your blog from 100 % of comment spam.
Check comment against the SpamBot Search Tool using the IP address, the email and the name of the poster as search criteria.