I foolishly had left trackbacks on by default on this blog. I just noticed that some of the articles had hundreds of trackbacks on them. I doubt this blog is that popular. I think I would have noticed if I got on slashdot. They all looked like link spam.
Unfortunately, Typo does not have any mechanism for mass deleting trackbacks. I had to go into the database and delete all of them. I ended up deleting 2045 trackbacks on only 45 articles. While I was at it, I changed all of the articles to not allow pings.