Trivial to bypass via spoofing. Nothing more than a very small bump in the road.You could always use Inclusive MAC address filtering. It is a bit of a pain, but you can block all network adapters except for the ones you specifically allow, then change your password. In some routers you can specify time limits for certain addresses to be allowed. It should be easy to figure out which computers have which addresses from the currently connected devices as it usually gives computer names as well.