Ouch! So in order for you not to be able to do anything at all until you agreed, it sounds like your ISP threw that at you? You get a similar thing when you buy a new cable modem and haven't registered it with your ISP yet.

I may be wrong here, but I think your actual modem also has a MAC address, so even if you change your Network card's MAC address, the data is still going through your modem with the unchanged MAC address that was sent the warning. I don't know offhand if you can or can't change the MAC on your cable modem.

Routers usually also have a MAC address in them that can usually be changed in the admin settings. Years ago (going on 7+ now) I wrote a Wardriving / Network utility named "WarDrive ToolBox" and one of it's features was to allow you to change the MAC on your NIC (Network card for anyone who doesn't know already):

Going on rusty memory you can edit the MAC in a registry key but the original MAC of the NIC is still hard coded on the card, so if the registry key is deleted it'll just revert back to it's original one, but if whatever is trying to get the MAC address see's the registry key it'll use that one first.

So anyway, to answer your question a MAC address is basically the same as an IP address, but for your hardware: any hardware that passes network data through it (NIC card, Router, Modem, etc.) it identifies uniquely that particular device. That's also one of the ways that alot of routers will allow you to tighten security to your wifi, you can set it in the admin area of your router to ONLY allow connections from white-listed MAC addresses. For example, you could choose to block all MAC addresses except the one from your Android Phone / iPhone / iPad, etc., which all have their own MAC addresses as well. If the router see's an OK's MAC address it'll allow the connection, otherwise "Go Away, Private Property Sucka".

That's what my utilities' feature was designed to get around ... if you were wardriving, and found an open wifi that you couldn't get on, with a little packet sniffing you might be able to change your MAC address to match a white-listed one and get into it.

As far as whether or not changing the MAC address will protect you from any more ISP notices, I'm not sure, but I'd really be interested to hear more from anyone who does know for sure, or if you find out more on it. I'm thinking that since there's a chain of MAC's (starting at your modem, through your router if you have one, then to your NIC card) it may only work if you were to somehow change the MAC of your modem, which is how your ISP identified and put the banhammer on ya, but again this is all just speculation on my part.

Trying to catch up on Game of Thrones maybe?

Here's an interesting read on HBO poisoning torrent downloads, and this site may help for blocking the blockers.

Thanks for the advice. I can change my computers MAC and the router ( i think) but the cable modem, no touchy!

Oh well, still do what i do just need to be smarter!

And YES! G.O.T is the best, it was worth it...

Thanks sDc