Menu Sign In Contact FAQ
Banner
Welcome to our forums

Can cellular networks detect if a phone is tethered to a laptop?

This question arises with the use of 3G phones which can act as a WIFI access point, and provide internet access for other (multiple) devices.

With Nokias you have the Joikuspot app which does this quite nicely. I think Iphones/Ipads can do it natively if purchased factory-unlocked, and definitely if hacked.

I don't see how the cellular network can detect the use of tethering. They could potentially detect that you are using some client app which cannot exist on a phone (e.g. IE9) and this has been much discussed here in the UK, but the "word" from inside the business is that doing that would be far too complicated, would generate far too many false positives (many laptop apps are available in phone versions, etc), the user can change the browser ID string, the user could hide all his activities by using a VPN (which phones do support), but the source did say that if they get somebody who is abusing his "fair usage policy" then they might look at the data.

Does anyone know any different?

I've never had a problem but there are reports of various issues which might or might not be related.

Administrator
Shoreham EGKA, United Kingdom

Never heard of it being a problem. If they could stop it they would.

EGTK Oxford

The networks supposedly don't like it (e.g. some Nokias sold in the US have the Joikuspot installation blocked) but they ought to be getting more relaxed about it these days.

The bottom line for a network is that the user is more likely to use more data, with a laptop tethered to a phone, than with a phone alone.

That's why e.g. a SIM card sold with a USB-3G adapter is likely to be provisioned on a "worse ripoff" tariff than a SIM card sold with a phone, or sold by itself. But you have to be pretty uninformed to fall for that one!

Administrator
Shoreham EGKA, United Kingdom

I believe it is a function they can program into the simmcard. Thus even if you have an Iphone which is perfectly capable and you go to .. for example the US and get a prepaid simm, they can lock this function so that your phone cannot use this.

On the Iphone they can definitely suppress certain config menus (the APN being a popular one) by putting stuff on the SIM card. That's a fact.

But how can they block tethering? It's implemented by an app which runs off the network connection (the socket) created within the phone O/S and which routes wifi packets to that connection.

Administrator
Shoreham EGKA, United Kingdom

In theory there is plenty the network could do to detect what device is being used. These are much more sophisticated than sniffing the browser user agent string which as you say would be easily circumvented. For example TCP/IP packets will typically reveal the OS that has generated them. That would work pretty well in this case and would even work if you were running a VPN which would otherwise shield the traffic from identification.

In reality I doubt they bother. Instead they just look at volumes of data and the rate of transfer. After all, that's what they actually care about. EE have taken a reasonable approach with their 4G service - you get a limit and how you use it, on your phone or tethered to a laptop is entirely up to you.

Administrator
EGTR / London, United Kingdom

would even work if you were running a VPN which would otherwise shield the traffic from identification.

How would that work, given that the VPN goes between the phone at one end, and say your home router at the other end?

If the VPN went all the way out to the tethered laptop, then I'd agree.

Whether any phone is capable of tethering over a VPN is another matter... I don't even want to think about repeating my VOIP experiment over a VPN

As regards data volume, I don't know this but I would have thought that the biggest data volume issue in the mobile business is people watching videos. Nothing comes even close. Video usage seems to be what kills the wifi in most hotels (no; I have no idea what kind of movies people are watching). And a smartphone is pretty good for videos.

Administrator
Shoreham EGKA, United Kingdom

I meant if you run VPN software on your laptop,with the far end point being whatever (a home or office router, or a VPN service) then the phone company can't interpret your traffic and certainly couldn't see, for example, browser user agent strings. But if they used TCP/IP implementation detection they could detect it was a laptop rather than a phone which had generated that traffic. Like I said though, I doubt they do it.

Administrator
EGTR / London, United Kingdom

Well, in the UK on Three - they do bother. I tried it a couple of times with my iPhone (bought outright, not network-subsidised) and received a rather stern SMS a few minutes later telling me I'd need to buy an add-on to my existing contract if I wanted to use it as a hotspot. I don't really need this, so didn't bother, but the bottom line is - yes, they can!

Someone told me that the Iphone loads a network configured 'tethering URL' when it begins tethering... so in effect it tells them you are doing it.

For the Iphone, that would not be suprising.

Administrator
Shoreham EGKA, United Kingdom
35 Posts
Sign in to add your message

Back to Top