ULib is a library that provides extra functions and utility to coders for Garry's Mod.
ULX is an administration mod. It uses ULib, but the two are separate.
Also, if you wish to find someone's IP address type 'status' in your console. this will return everyone's IP / SteamID / UID / etc etc etc.
To ban an IP address I believe the command is addip <ip address> if you type in addip and hit enter it should tell you what else is required to use the command.
I would recommend banning by STEAMID though as IP address often change frequently.