This simple server mod allows Super Admins to place IP bans with a few commands. Basically if a player connects under a banned IP address, they get permanently banned instantaneously.
/IPBan <Playername> - Kicks a connected player and adds their current IP to the IP ban list.
/BanIP <IP Address> - Bans a specific IP address.
/unIPBan <IP Address> - Searches the IP ban list for the given IP address and removes it if found.
/unBanIP <IP Address> - Alias of /unIPBan.
/listIPBans - Shows all available information about current IP bans.
/changeIPBanMode - Toggles IP ban mode between the 'ban' mode and 'block' mode. (Ban is recommended. Only use block if you're trying to keep someone from lagging the server with connection attempts.)
/CheckIP <Playername> - Get the IP of a player in the server.
Extra credits:
Jakob - Test Subject.
dargereldren - Test Subject.
Böltster - Suggested this.
Rykuta, Jetz - Looking over my code, but ultimately not causing any changes.