Trackback Pings
If you're using Movable Type, disable Trackback Pings. Not only are they a major spam target, but the .cgi script that runs them is inefficient, and therefore a big drain on your server (especially when, as recently, spammers have been hitting it with upwards of 2,000 pings an hour).
HOW TO DISABLE TRACKBACK PINGS
1. In your MT Weblog Config/Preferences, make sure "Allow Pings on by default?" is unchecked.
2. Diable the trackback script. This is very important: if you don't, spammers will still hit the script thousands of times an hour, which will cause a continual drain on your server. In your main root MT director, either delete the "mt-tb.cgi" entirely, or use your FTP program to set permissions to 000. In a graphical interface such as GoLive, uncheck all boxes, which will look something like this:
Remember to click "Set Rights" after unchecking the boxes.