Before we get to methods to fight comment spam, it is very important to understand how spammers and spambots work, what methods they use, what types of comments they are posting.
Any WordPress website that allows comments or implements forum (bbPress or something else) attracts comment spam. If you ever wondered how comment spam finds your website, this is a good place to start.
GD Security Toolbox Pro is a new Dev4Press plugin dedicated to hardening WordPress security. Plugin monitors security related events and includes wide range of tools to trap spammers and stop malicious attempts.
GD Press Tools Pro 5.0 is coming along nicely, and at this point, all of the plugin features are outlined and already completed or in development. This post lists all the planned features along with plans for GD Security Toolbox Pro plugin.