It would be great if it could not just allow you to delete all of the posts and ban the accounts with the same IPs, but also do a secondary search and look at all of those account's IPs, and then allow you to ban them as well.
User1 with IP 1.x.x.x and 2.x.x.x spams the forum. You ban them like normal, and the tool finds:
User2 with IP 1.x.x.x and 3.x.x.x
User3 with IP 2.x.x.x and 4.x.x.x
User4 with IP 3.x.x.x
User5 with IP 4.x.x.x
The primary sweep would find User2 and User3 (like it already currently does) and mass bans them, but also checks their IPs and finds User4 and User5 and allows you to mass ban them.
The tool could also be set so that if a certain IP has greater than X number of spammers on it, it would add the IP to the blocked range list (optional of course).