IP Blocker Firewall from BeeThink.com
This program is fantastic!
If you run a server you know you are constantly under assault, whether it is email server attacks or other types of attacks from the outside.
Our email servers and applications were getting hit so often the server was slowing down. They didn't get in, but it was a major problem.
We installed IP Blocker and customers started emailing us, asking what we did to speed up the server.