Those of you who run popular websites have had to deal with comment and trackback spam. Many tops sites have migrated to Disqus and other commenting platforms already. Even in that case, you could end up with spammers targeting your site. While WordPress allows you to turn off link notifications from other blogs, you will have more work to do to completely stop trackback spam. Here are 2 ways to deal with it:
Simple Trackback Disabler: this plugin lets you clean up unwanted trackbacks and execute SQL commands to disable comments and trackbacks in bulk.
MySQL: this is the easiest way to deal with the problem. You will simply have to open phpMyAdmin, go to SQL, and run the above command. You can also modify the above query to target only specific posts.
There are more complex ways to stop trackback spam (e.g. with Apache and Nginx directives) but we have had the most success with the above methods.