The blog comment/trackback anti-spam refinement continues.
But trackback spam is still a problem. One available option is to block direct access to the WordPress trackback PHP, but this isn’t very effective, since most current trackback spammers however are clever enough to call the “real” URL.
A version of Auto shutoff comments modified to close trackbacks on posts older than 28 days, however, seems more effective. I don’t particularly want to shut comments off (especially since the above plugin effectively stops comment spam), but trackbacks are less compelling to keep open.
Together with previously discussed .htaccess entries to block big bandwidth thieves, this appears to be a fairly effective set of anti-blog spam measures. For now.