Still Perfecting the Spam Blocker

Thursday, August 25, 2005, at 10:39AM

By Eric Richardson

I wrote recently about my first and second steps in fighting comment spam. In the two weeks since I put those measures into place I've blocked 3400 requests to this blog and 4755 requests to blogdowntown.

I also put in a third level of blocking sometime between then and now, adding a RewriteMap that lists specific problem IP addresses. That's great if the spammers are reusing proxies, and if nothing else it just makes me feel like I'm doing something. That list is now up to 62 IP addresses.

And now today I've added a second DNS check, this time to query This list is designed to target open proxies. It's not perfect -- it only lists 17 out of the 62 IPs on my deny list -- but it has better coverage than And defense in depth is never a bad thing.

So basically I have no problem with referrer spam these days, but comment spam still trickles in.