Here’s a better hack from WordPress user, LisaS. It forces all trackbacks into moderation. http://wordpress.org/support/topic.php?id=20106
Thanks! I got hit by this yesterday. I renamed the trackback script as soon as I noticed the spam trackbacks (the first one was gibberish, but the following ones were nasty porn sites with highly offensive text in the trackback). I’ll give Lisa’s suggestion for moderating trackbacks a try.
A growing list of methods to combat trackback spam is available at the largest (unofficial) WordPress anti-spam resource.