Spammers!

So I’ve had my ThinkPoint Blog site up for awhile now however recently this one spammer has targeted me every day! Everyday he/she posts like 4 comments on a random page from multiple IP addresses leading me to think he’s hijacked someone else’s computers. Also, some of the links he spams are really sick… Like granny sex… WTF? Also, why is he spamming my blog? What traffic does he get out of it when I delete it right away… Anyhow, I’ve tried to IP ban him, however those IPs aren’t his IP, and so I can’t actually stop him… What can I do? BTW, I’m using Wordpress for my CMS.

Thanks