Elise.com has a thorough discussion of techniques for fighting comment spam. What seems to be the most widely used is Jay Allen’s mt-blacklist. But since that would have required an MT upgrade, I opted to first try this simple hack. It is based on the assumption that there is brainless automation on the other end of line.
Rename the “mt-comments.cgi” script in your mt directory.
Find all references to “mt-comments.cgi” in all of your templates and rename them to match the new name you gave the file.
When people send you email saying they tried to post a comment and got a “couldn’t find mt-comments.cgi” error message, go back and find the templates you missed.
Update March 30, 2004: This didn’t work. After five days, two different spammers, including one of my old regulars, were back.