Ban spammer IPs from comments section

The spammers have changed tactics again; now they’re not including their spam in the comment, but are putting the spamvertised link in the URI field so it isn’t caught by the spam filtering options.
At the moment I’ve got a scumbag posting one of these comments on EVERY post, starting from #1. Now I’ve banned the IP in my .htaccess file.
Getting to the point, it would be very useful if we could add banned IPs to our .htaccess file using an option by the IP field in the comments admin section.
OK, in the long term they’ll just change IP. But in the short term, it stops them from being able to do every post in one go.