If you are using Spam Karma 2.2 or above you shouldn't need this plugin.
In my never ending fight against comment spam on this blog I have installed a few different plugins. The most recent is Spam Karma 2 written by a guy dubbed "Dr. Dave". It is pretty cool and extensible. That means if you want you can add your own plugins to the plugin to help fight the types of spam you are seeing. For instance my blog has been getting a bunch of anonymous posts with no content - to me that is spam. So, I cranked out a very simple, and easy Spam Karma plugin titled "Blank Comment Detector". If your using Spam Karma 2 then feel free to grab my plugin.
Download the Blank Comment Detector Spam Karma 2 Plugin
To use the plugin just drop it in your SK2/sk2_plugins directory, go to your Spam Karma 2 general settings page and hit save. That is about it.
Boy, I stink. I had to update the plugin already. I didn't realize i wasn't providing a log message for why the comment was getting hit as spam. So now the plugin logs its action properly. Just redownload from the provided link and all will be right with your installation.