Disable trackbacks for post doesn't work

I’m currently flooded by spam from the Ukraine. All comes in as comments to a single post. Since the comment form would not accept the chosen user names, it must be trackbacks.

So I unchecked the trackback and pingback acceptance for this post. But the spam wave didn’t decrease.

I meanwhile added a detector in the pre_comment_approved hook, which marks all these things as spam immediately. But I’d expect the checkmark to do the work and do not crowd my database with spam comments.

So, before I claim that the checkmark is buggy … is there a way to figure out how the comments entered the system, i.e. as trackback, as a logged in user, or as guest comment?

Thanks for your help,
– laotzu.