Site config and blog spammers

I’ve been trying to figure out why I am seeing so many 404s in the logs. It doesn’t seem to effect humans, but search engine bots and comment spammer bots seemed to be having a hard time. That wouldn’t bother me, but it was hurting my ability to send trackback pings to myself.
I changed one thing and now trackbacks seem to be working a bit worse, but the spammer comments are getting through. Really, I wanted that. The blog software is stopping it effectively. I’d rather the blog software stop the spammers than a misconfiguration. Now, I just need to find some time to fix the trackbacks. I have it set up so outbound trackbacks occur on links to this site and myitforum.com/blog only.
Really, you’d think the blog spammers wouldn’t even bother attacking version of software known to have spam filters.