I just read in vodafone Greece website that the free Megabytes on their talk plans are only available for smartphone use and that if you use the phone as a modem to connect your pc or laptop they will charge you differently.

How can they know if I am using my phone as a modem for itself or my pc? If there is a way for them to know, can we spoof it? Maybe use the phone as a proxy of some kind. Can it be the User Agent string of the browser? But then if I download some torrents what?

btw their smartphone internet plan is 20eur/month unlimited while the pc internet plan is 50. Could they be writing all these to scare you off from using a smartphone plan for pc access?

Any ideas appreciated
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Asianplaydoll live

if you're using the phone as a modem (not using MHS/Joiku as "proxy"/router) then they can easily determine your laptops OS from the "tcp fingerprint" (should they actually care enough to look).

user-agent is also an idea but requires deep-packet inspection which is "computationally expensive" (or running a transparent web proxy between customers and internet but thats not foolproof either).

when using the phone as router there are still ways to determine some things about the machines behind the NAT done by the phone.

and of course they can say that the smartphone plan is meant for checking email; not running torrent client on the phone... and due to "excessive use" you either upgrade your plan or they choose to no longer serve you... the boilerplate contract language is such that they don't need to actually prove that you were using the phone as modem/router.

why should I choose the unlimited plan only for checking e-mail? Anyway OS fingerprinting could also make the N900 seem like a computer since vodafone greece is unaware the very existence of the product, and in general it's running linux.
If I get it correctly you suggest that using MHS is a way to spoof it. What about bluetooth DUN?
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SunnyApril cam

An easy method to make a difference is the APN setting.
If you use computer, usually there are some predefined net settings per provider, while on the phone you receive them through the sim or by sms.
I've seen some opertors to distiguish between enterprise and mobile users and open/close different ports ...etc.
This just a possible sujestion, I don't know how you operator is actually doing it.

I tethered my n900 (on AT&T) for a whole week when my home internet was down and nothing happened...

Android and iOS use different APNs for tethering and mobile browsing. N900 (Joikuspot, etc) use whatever APN you choose. Vodafone Greece won't know you are tethering.

Στο λέω σίγουρα γιατί το έχω κάνει :Ρ

That's good. Ubuntu let's you choose the APN you use when you Bluetooth DUN your phone so i'm safe this way.
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SweetJennifer cam

They might monitor your usage pattern, and if you do stuff that you wouldn't on a normal smartphone (e.g. bittorrent, heavy downloading) they may pick up on it. And they charge different rates for smartphone and pc access because they know a smartphone user will typically use far less than someone on a PC. If you keep your usage at a reasonable level, I doubt there will be any problems.

I don't know how operators get away with offering "unlimited" plans that are blatantly NOT unlimited. Why isn't anybody in the civilised world suing these shysters for false advertising?

DUN == using the phone as modem (vs router).

and yes, os fingerprinting makes the phone look like linux computer, however as I said it's far more likely they just say your usage pattern is "excessive" and upgrade of plan is required.