Akismet

smet is a plugin for Wordpress, a popular open-source content manager. You can use it to filter out spam and other unwanted comments on your blogs. It works like this: whenever a comment, trackback, or pingback is posted on your site, it's sent to the Akismet website, which tests it and sends back either a favorable or unfavorable result. With Akismet, you don't need to keep a black list of spammers any longer. This web service takes care of everything. If you happen to receive a false positive, you can always get in touch with Akismet to get a different result. To use Akismet, you need an API key, which you can get on the user registration page on WordPress. Click here to access it.