Please dont block IP addresses. It is completely useless and hurts genuine users. The spammers dont use static I.P's. They use dynamic I.P's. When some non spammer uses that I.P then they too will be blocked.
There have been times when I have gone to some sites only to be blocked because my I.P has previously been used by some spammer. It's my loss and the sites loss as well.
I do not block IPs until I first search to see if any legitimate users would be caught also. We have some spammers who are using the same IP all the time and those are the ones I blocked. I also only block them temporarily. I am hoping that being blocked will stop them from coming here and then I can unblock the IP.