Whilst researching ways to block trackback spam, I had a look at using .htaccess to deny access to the trackback URL for each post. Just in case you’re interested, here’s how it’s done. Add the following lines to the top of the .htaccess file in your blog directory.
SetEnvIfNoCase Request_URI "./trackback/" not_allowed
<Limit GET POST>
Deny from env=not_allowed