You can just take the cat 5 cable that the cable modem connects to the computer, router and or hub. You could also delete (remove) the tcp/ip protocol for the NIC (network card or usb). You could always take the Coax Cable and unscrew it from the cable modem and wall. Theres alot of ways you could make it where no one can use the cable modem. But mostly you could just disconnect any cord that makes it where the power, cable, or pc light doesnt light up on the cable modem.

I help people get connected to the Road Runner Service.... Never helped someone get it where they couldnt get on before though I wish I could for some people that call us up.