NerdKey

Created to work alongside the NerdTools Bad Bots Spam Reporter & Spam Defender plugins, this plugin will read all comments posted to detect common spam elements and proceed to mark the comment as “spam” automatically if a match is found.
More information can be found at http://www.nerdtools.co.uk/badbots/

NerdTools Comment Filter

This plugin will read all comments posted to detect common spam elements and proceed to mark the comment as "spam" automatically if a match  …

Powered by NerdTools.co.uk, this plugin will automatically and anonymously check the authors IP address against the NerdTools Bad Bots Intrusion & Spam Detection database.
If a match is detected no commenting will be allowed and a custom error message will be displayed instead, if no match is detected commenting will be allowed as normal.
More information can be found at http://www.nerdtools.co.uk/badbots/

NerdTools Bad Bots Spam Defender

Automatically denies comment access to known spammers in the NerdTools Bad Bots database.

NerdTools Comment Filter vs NerdTools Bad Bots Spam Defender