I’m getting enough comment spam now to warrant writing a script to redirect them, is there any one out there that is interested in using and testing it when it’s done, unfortunately this will be for PHP capable hosts only.
Up to now the WordPress comment spam filter picks them up and puts them into the ‘awaiting approval’ queue which is fine if you only get a few but hopeless if you get more than a few and need to check for false positives.
After a bit of investigation I’ve found that most of the spammers are using annonymous proxies so there is no way to filter using REMOTE_ADDR, REMOTE_HOST, HTTP_VIA, HTTP_X_COMING_FROM, HTTP_X_FORWARDED_FOR, HTTP_X_FORWARDED, HTTP_COMING_FROM, HTTP_FORWARDED_FOR, HTTP_FORWARDED, HTTP_REFERER, or even HTTP_USER_AGENT as they either don’t exist, are easily spoofed, or are the proxies address which they change at random.
I finally found out how to query the lists of spam servers and open proxies that mail servers use and will write a PHP class and associated include file to run it. If the potential spammer appears in over a certain number of the lists I will return a 404 error otherwise if they only appear in only a few lists they will be redirected to a page explaining what has happened in case some one’s ISP has ended up on one of the lists.