Unb-plugin-stopforumspam is a project mainly written in PHP, it's free.
A plugin for UNB to make use of the stopforumspam.com API
Stop Forum Spam Plugin for Unclassified Newsboard
This plugin checks the provided username, email address and current IP address of anyone who attempts to register against the API provided by http://www.stopforumspam.com
If a match was found, the user registration will be denied. Denials are logged in the standard UNB log.
To install copy the stopforumspam.* files into your unb_lib/plugins folder.
Copyright (C) Andreas Gohr [email protected]
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
See the docs/license.txt file in your UNB folder for details