If you’re using Movable Type 3.0x, you’ll probably want to install the emergency release of MT-Blacklist v2.0e. I’ve experienced a glut of comment spam, which I’ve been able to keep under control only because I go in and perform Operation Clean Sweep (name that movie reference!) every night.
Here’s a hint: “Sandman to Viper Command, we have detonation over water. It may have been wind shear. Over.”