Sir-Uli

This plugin provides a possibility to block comments based on words of a predefined list. The built-in lists of wordpress only allow to send comments to the moderation- or to the spam-queue but not to block them completely. This is remedied with this plugin, which allows to block comments based on a definable list.
Attention #1: Use wordlist with care, there is no logging of the blocked comments!
Attention #2: It will also match inside words, so “press” will match “WordPress” as well!

WU – Block comments

This plugin provides a possibility to block comments based on words of a predefined list.

Garth Mortensen

A plugin that interacts with the StopForumSpam.com api to protect your 
website. Find out how many unwanted attempts have been blocked in Dashboard > 
Tools > Seriously Simply Spam Blocker.
<h3>Usage</h3>
Simply upload/activate the plugin and you’re good to go.

Seriously Simple Spam Blocker

A plugin that interacts with the StopForumSpam.com api to protect your

WU – Block comments vs Seriously Simple Spam Blocker