My blog isn’t terribly popular but I do have a good number of links to my plugins which has made me a more visible target for comment spammers. The built-in WordPress spam filter does a pretty good job but it does nothing to stop bots from hammering my blog and eating up bandwith. One of my friends in my extended blog network had a post that tipped me off to a more active method of spam prevention, Bad Behavior.
Bad Behavior works by analyzing the HTTP requests made by clients and running them through a set of tests like checking the user agent description. Before installing the script I was receiving about 200 spam comments per day and maybe 1 or 2 would slip through per week. Now I’ll get maybe 1 a day in my spam queue. Not sure how much this affects the bandwith the spammers are using but it will definetely save a little on database.