Killing Comment Spam

While some other blog software has had comment moderation before, since I use a completely hand-written CMS, I needed to implement it myself. I've been having quite the problem with comment spam recently (as any of you with RSS readers has seen, I'm sure), but hopefully my solution will fix it. Of course, I can't discuss it or it makes it very easy for the spammers to work around it. We'll just have to wait and see, I guess.