2006/9/18, Gabor Hojtsy <gabor@hojtsy.hu>:

We have some .htaccess directives at weblabor.hu to cut down on pointless
CPU usage. One is denying requests based on referers (which is trackback
related too).

SetEnvIfNoCase Referer ".*(casino).*" BadReferrer
SetEnvIfNoCase Referer ".*(pharmacy).*" BadReferrer
SetEnvIfNoCase Referer ".*(gambling).*" BadReferrer
SetEnvIfNoCase Referer ".*(poker).*" BadReferrer
SetEnvIfNoCase Referer ".*(pills).*" BadReferrer
deny from env=BadReferrer

Also if you would like to send a proper(!) "Gone" HTTP code to user agents
who try to request your previously available trackback URLs, you can do:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^trackback - [G]

This sends a "Gone" HTTP status to the requester. This is better then an
"Access denied" status, since you explictly state that the resource does
not exist anymore, and any reference to it should be removed. The actual
difference in meaning is only relevant for well-behaving bots, not the
spammers, but it is nice to accurately inform well-behaving bots about the
situation.