Can the ISP block Internet Connection Sharing?

[taher]

Hello,

The ISP that provides us with internet has given us an IP address to use to access the internet. And we had 2 computers at home, so we thought about Internet Connection Sharing. Directly plugged in another network card, enabled internet sharing and started browsing from the other computer when an error page was showing telling us that internet sharing is not allowed and there's like 2 police officers catching someone (they caught us, bravo :p).

Anyways, I was interested in the technology itself since I'm a system engineer myself. I wanted to know what software/hardware might the ISP be using to deny internet sharing. I thought of cookie-based IP address check, the time-to-live also changes when you are behind a gateway. Tried to google but was unlucky. So I thought Neowin might be able to give some help.

Thanks in advance.

--

Regards,

Taher.

[xpablo]

Your isp can't block ICS, because ICS is internal. if your ISP only gives you one IP and you want to split the connection you would be better off investing in a router, then you can network your pc's better. this would be a much better solution than using ICS.

as for your error page I suspect that's some 3rd party application on one of the pc's.

Also are you using a crossover cable between the 2 computers ?, this could be your problem if not.

for more info on ICS.

http://support.microsoft.com/kb/241570

[taher]

xpablo, thanks for your answer. Just wanted to remind you that I'm no newbie here. I'm a systems engineer and internet servers is my specialty (ISA, StarOS, Mikrotik, etc...). But I saw this on a user's pc (note: there's no client software on any machine whatsoever) and first thing that came onto my mind: I need that software.

I'm thinking more how could it have been done and i thought of this: The proxyserver could embed a javascript into every webpage requested and then the function inside the javascript is executed with body onload. This function might forexample check if the IP on the machine is different from the IP which sent the request. If that is the case, it redirects you to a webpage showing that you are blocked from using internet.

It could have been made differently. I just thought of one way to accomplish this. I still need to know what software can help me do it.

Edited March 22, 2007 by taher

[Japlabot]

doesn't sound like javascript to me, too unreliable. Probably something simple but effective

I think that the ICS reverse DNS lookup can disclose the real hostname of a machine, but I'm not sure as I havn't used it in a while

try https://www.grc.com/x/ne.dll?bh0bkyd2.. but I'm not too sure if that's a good example

Which ISP?

[atomicski]

i find this very hard to believe, it has been brought up before, and i still think that if it is even possible for an isp to find this out, it would be way too much work to practically use, and plus, it would be super easy to spoof and get around it. i'm sure theres a way to set up a proxy in your house to make it look like all requests are coming from it.

[Farstrider]

Please correct me if I am wrong, but I cannot see the point of an ISP doing something like this! What would the difference be if you have one account, that for arguments sake has a 10Gig cap, the line is in your house and you use the full quota for the month, what would it matter whether or not one PC in the house has used it or 10 PC?s? You still pay for the account so why could you not use it as you see fit! What happens if I have an account at home (ADSL) and I use it on my laptop via a wireless connection how is the ISP going to stop me? They can?t, that the answer, and as far as I am concerned it is not illegal!