Is there way to ban NET Modem and IP?
Sure they can change, edit IP's with tons of programs but what about this since I was GM in few games that had this feature.
Plus they had feature that send information about your PC + IP + Location to server host and log and if you get client banned, that client can not run on that PC ever again.
The problem is you don't really get informations about the client side. Only ip and if you programm you game client so that you could get pc name but that's it. Also in the case you get a "PC ID" they could just change it into something random before it gets send to the server so it's "impossible" to ban someone so that he can't play that game again. The best thing you could do is ban all his chars so he will lose the motivation to play.