Referrer spam on this site is increasing daily. Until now I use a two-step method to block them, even though I don’t publish my referrers. First of all, I maintain a list of used domain names. I check my referrers every day, and add newly found domains to the list. If a visitor uses one of these domains as referrer, the request is automatically blocked, and the IP address of the visitor is automagically put on a second list, making sure that future visits will be blocked as well. IP addresses stay on the list for one month, to make sure the size of the list does not get out of hand.
I noticed that the domains on my list are all mentioned in the MT-Blacklist. So those referrer spammers are also comment spammers. MT-Blacklist is updated automatically from the clearinghouse, so needs less maintenance. It would be nice to be able to combine the two methods right?
Today I found derefspam.pl, a script to use the MT-Blacklist to remove referrer spam from your server log files. At first thought I wanted to install it, but then I realized that all this script does is throw away information, so it won’t pollute your statistics. Since I want to be able to see what really happened on my server, I prefer not to throw away this information. After all, these requests have consumed some bandwidth… A thought was to implement a script for each request, but I am sure that this will slow down my site too much, since database requests take time… For the moment I stick with my two lists, and hope that spamming will decrease soon.