Ban someone, and then it might appear, at least it did for me.
addip <ip here>
writeip
Those should add an IP into a ban list, then you can add more, because I believe that adds a ban file under what b00n said. Then just open it up, and add more bans into it through the .txt file. Also if you create that .txt file, i think you can just put an IP in there? I can't check atm.