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I've got 2 sim cards from the same mobile network provider with the same "unlimited" data plan.

Card number one works great when tethering from an android phone. And also from a 4G router (mifi) device.

Card number two sometimes works with that very same android phone. But get's blocked when I use a 4G router (get redirected to a web page stating that I'm up to no good). Sometimes, when tethering from an android phone, I get very slow speeds (<1Mbps down) but very fast speeds from the phone itself.

I know that it is possible to know when someone is tethering (something to do with TTL) but how exactly do they do it?

And why does it work for sim card number one but not for sim card number two with the same data plan?

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  • Does that post answer my question? "why does it work for sim card number one but not for sim card number two with the same data plan?" No. Is that answer related to a 4G Mifi router? No. Is my question Android speciphic? No. So...Why is this question still on hold? The question is still not answered. There is still no explanation for why the same data plan is serviced in different ways.
    – Txugo
    Apr 29, 2016 at 8:43
  • "Why is this question still on hold?" because it is off-topic for Super User.
    – DavidPostill
    Apr 29, 2016 at 8:46
  • it was off-topic for Server Fault. it is off-topic for Super User. It is certainly off topic for android. So...where is it supposed to fit?
    – Txugo
    Apr 29, 2016 at 9:02

1 Answer 1

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1 - TTL detection: If the value of TTL is less than the expected value, they can assume that there is tethering. However you can tweak Windows / Linux to send a higher value than usual.

2 - User-agent sniffing and OS fingerprinting: When your browser requests a page, it sends its user agent, version and other parameters. Networks can detect if the version of Chrome or Firefox is a desktop version. The other thing that is easy to detect is OS. Check this if you want to know how much they can detect of you.

3- Traffic/port sniffing: Networks look at what UDP / TCP ports you are using and what kind of traffic is going over them. So they can detect videogames, bitttorent, etc.

Using a VPN you can at leat disguise your traffic in a way that it is harder to apply all these techniques.

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  • Different mac address also, it sees a different device other than the phone tied to the account. This is the main way they detect tethering other devices.
    – Moab
    Apr 28, 2016 at 15:28
  • The crucial thing here is "why does it work for sim card number one but not for sim card number two with the same data plan?" but thanks for your answer
    – Txugo
    Apr 29, 2016 at 8:44
  • I've tried using vpn with the same results.
    – Txugo
    Apr 29, 2016 at 8:45

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