#1: If the cable provider doesn't allow multiple logons, it doesn't matter how you disguise it, they'll find out and (possibly) disconnect you. Worse, some cable providers consider this fraud and will report you to the police for "theft of cable service". There was a somewhat infamous case a few years back where the guy was in and out of court for 2-3 years even AFTER the ISP asked the police to drop the case.
#2: It's a dumb rule because that's what speed caps are for. Many/Most providers use a filter at your access node to restrict your d/l speed to some reasonable figure like 384MBS so they can "guarantee" you this share of each cable subnet they install. If there are 10 users on the subnet they assign 3.84MBS to the subnet and don't worry about it further. Then you can have 100 PCs hooked to the Internet in your house: Their throughput is going to suck wind is all.
Go to your providers website and read their Terms and Conditions of Service policy carefully. If it says you are not allowed to connect multiple PCs to your modem, don't do it. If it says the opposite, however, take it up with your provider. Don't just call a Customer support rep and complain; those guys are paid minimum wage to blow you off. Be able to point to the specific provision of the T&C to prove your case and you might put it in a certified letter to them.
If they haven't sent you a nasty letter or contacted you in any way I suspect it's really some kind of technical issue with your set up. As I said, most providers have speed caps or don't care. Do you have the modem connected DIRECTLY to your host PC and a 2nd NIC connected to the hub? I wouldn't think they'd be able to see that unless they were scanning your packets.
