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 only.
Really, you’d think the blog spammers wouldn’t even bother attacking version of software known to have spam filters.