They're back!
As you may recall, I upgraded to MT 3.121 to get Typekey registration and comment moderation. And I wanted comment moderation to stop the comment spam.
It worked. The comment spam has stopped. But the bots are back nevertheless; now they're sending trackback spam. Sexually vulgar trackback spam, no less.
It's irritating as hell and I've been aggressively deleting the spam. The bot pings and I delete. Ping. Delete. Ping. Delete. And so it shall be. No hair hole is using my blog to improve the Google ranking of his porn site.
Alas, in my haste to erase the smut, I accidentally deleted three legitimate trackbacks. To the authors of the posts from which those trackbacks originated, my apologies.