"Free Access"

Hello,
I have a question about free cable modem access.

About three weeks ago my friend moved out of the country and gave me his old cable modem. Out of curiosity I plugged it in and found that I recieved internet access! This lasted for three weeks but since Christmas eve I have not been able to connect. I was wondering if someone who knows could let me know how I might have been getting free access, why it might have stopped, if and how the cable company can track people getting free access (mac address on modem?) and if I will have any problems when and if I have to sign up for legit service.

Thanks.

Obviously, the IP sent to the modem by the Cable Provider has lost its lease. Your friend probably had a little more time left on his service but after the month or whatever the billing cycle period was up and there was no payment to continue service so the Provider sent out a 192 IP which disables the connection.