Most operators are probably running HTTP proxies (transparent or otherwise) and checking user agent strings in the logs would be trivial. Running something like p0f to fingerprint hosts is also quite easy.

so i take it it's possible for operators to find that out? and there's no way we can tweak our N900 to fool them?

sorry for the noob questions but this is the first data plan that i have. no other phone was worthy of a data plan before the N900. :P

@nokix - you'd change the user agent string on your desktop browser to throw them off.

just to say as well I've never heard of anyone being caught out by this.

It's not clear to me that they could really tell the difference between the N900 and any other computer. You can run OpenVPN on the N900 or your tethered computer and route all traffic that way. That would avoid http proxies and just about anything else. What other difference (from a traffic standpoint) is there between the N900 and any other Linux computer?

"Indeed you just need to click a button to use your N900 as a modem. At least in ubuntu, but it can't be that hard on windows either."

How many "average" people do you know running ubuntu??? My point was that it seems a bit odd telling people not to use there phones as modems when those that will be doing this will no doubt figure a way around it anyways...

I just dont really see how a teleco would be able to tell the difference between browsing on ur phone and ur pc...? Surely it's the same traffic? More so I just can't believe that these teleco's think that in some way this leads to larger amounts of traffic, surely the solution would just be "hey everyone use your phone for whatever you want, just dont go over your cap"??? Why do these companies insist on taking a stance that is proven not to work and instead creates this grey area where only the smart people can work there way around the issue.

In the end it just defeats the point of innovation, whats the point of a phone that can play flash, movies, music, allow for the user to always stay in contact with friends if the teleco's wont let you use youtube or msn?!?!

We might aswell all have stick with our Nokia 3210's!!!

Ok let me throw in some experience, since i am teaching Internet Security at the University

They could indeed detect the user Agent string from your Desktop/Laptop PC. It's quite hard to user Firefox 3.6.3 on your N900. But: As soon as you use a secured connection (VPN, ssh tunnel), there is no way they can detect it that simple.

TTL would be a possibility (FYI: The TTL Field in the header of an IP datagram is usually set to 128 and decremented by one on each hop). So when using NAT, the TTl fields of IP datagrams originating from your PC will be set to 127 when it departs from your N900. Still, if a phone operator tells, my TTL Fields are short by one, then i will laugh straight at their faces and request a traceroute with all connections to prove that they didn't mess up the routing.

So in a nutshell i'd bet you'll be pretty safe enjoying your dataplan with your PC/Laptop. The effort to prove you wrong is way beyond everything a few more bytes of traffic costs them. Maybe install a plugin for you firefox to masquerade your User Agent String, to be sure..

And as one of my previous posters correctly mentioned: If a phone operator says its not allowed to do something, 98% of all ppl won't do it. now, THATS efficiency

You don't have to actually run Firefox to send its user agent string. It's easy to change that string in most browsers (which you might do because you may not want the mobile-formatted site). Also, you can use the N900 like any other computer, and that means traffic beyond the web (rdesktop, vnc, ssh, etc).

well, this is what it says on the contract. i'll do my best to translate it.

"If the customer uses the mobile phone as a PC modem to connect to the internet or uses "SMC-Voda Broadband" (Internet) or other APN as the APN setting, a surcharge of $0.06/kB will apply."

what's the deal with the APN setting in this case? i remember if i am to use fMMS, i need to fiddle with the APN. does it mean the use of fMMS will fall into the category of "other APN"?

Capturing the data is trivial. But if you are aware of p0f you will be aware of its limitations. So first they would need to gather fingerprints of all possible devices that are permitted to use their service, and then compare against traffic seen, then double check any anomolies against firmware updates or any of the many different ways the fingerprint could have altered and then put it to the customer that they are in breach based on something so flakey. It sounds unfathomable that any carrier would do this.

User agent strings are the same. There are at at least four browsers I can run from my n900 and with any of them I can set the user agent string to whatever I like. There is nothing in the t&c that stipulates that you must use a specific user agent string I presume. Repeat for all user agent strings for all valid browsers for all handsets.

Neither effective or likely.

Is the "SMC-Voda Broadband" APN different to the APN the phone uses to connect?