I'm really surprised it took this long but I finally heard people are receiving trackback spam. Comment spam, leaving bogus comments on people's websites advertising stuff or sites was first. It became easy to automate because lots of people are using the same software to run their website therefore write a script to spam on and you can spam all the same sites..
But, Trackback is even worse. Trackback is a standard the lets a computer programatically leave a comment on a site if that site supports trackback. It was a way to promote cross site discussion. Unfortunately the standard has no way to deal with bogus comments or spam and it runs the same on all sites that support it regardless of software specifically because it's a standard
With plain old comments you can do all kinds of things. You can customize your form so it's not the same as everyone else's. You can add one of those "type in the code you see below" things. You can require registration before posting. You use something like Typekey (global registration). Etc....
But with Trackback. It's a standard for the computer therefore it can't change. Change it and you break the standard and the other computers won't be able to connect. So basically, all those solutions are out. The only solution is a new standard. Trackback 2.0?
Turn off your Trackback feature before it's too late. I did today 😞