Kicked of net,new security?

[Vrisak]

I been using cloned modem for few years now,geting kicked from net after few minutes,telnet saying Bandwitch request failure 0,my question is did new security sistems somehow can track MACs from diferent areas, i should test it with diferent MAC, but geting working MAC with serial number can be realy painfull (specialy if your friend who gived you mac and serial stoped paying ISP). Any help will be apreciated just dont know in witch direction to go.