SysAdminGear

Spam Firewall is a plugin for Movable Type that can help reduce this load. Spam Firewall want to block 80% of spam attempts before they reach Movable Type comment and trackback scripts.

Spam Firewall creates a PHP script that acts as a firewall. Once installed, when comments or trackbacks are posted, they get posted to the PHP firewall script.

The Spam Firewall will scan the the request against a list of common spam patterns. And if the request matches, things stop right there. If the request passes the test, it gets forwarded to Movable Type for processing in the normal manner. Most spam is blocked quickly with Spam Firewall, without consuming large amounts of CPU and memory.

Requirements:

- Movable Type 3.2+
- PHP (Note: you do not need to enable Movable Type dynamic publishing to use Spam Firewall.

(via: http://mt-hacks.com/ )

Spam Firewall Instructions