Spam Karma 2 (SK2) is an anti-spam plugin for the WordPress blogging platform. It is meant to stop all forms of automated Blog spam effortlessly, while remaining as unobtrusive as possible to regular commenters. Spam Karma 2 is the proud successor to Spam Karma, with whom it shares most of the development ideas, but absolutely none of the code.
For installation you need a Wordpres 1.5.1 or higher and MySQL 4.0 or higher.
Download it from here.
I would strongly recomended it to you. 😉 The offical site is here.
P.S. At the botthom of my site you can see a sign that my page is protected by Spam Karma 2. 😉