[aklug] Re: off-topic: android ACS tech-savvy tech support?

On 07/05/2011 11:15 PM, adam bultman wrote:
>
> On 07/05/2011 05:46 PM, Shane R. Spencer wrote:
>> I'd be interested in knowing how they can detect rooted phones if the mobile network is
>> simply an ethernet interface on the phone. Which it is. You can't even detect tethering
>> at that point without scanning the traffic to find requests that are obviously not being
>> delivered to a mobile web client - which is utterly inconclusive.
>>
> Shane, I know we talked about this. I can't necessarily tell regarding
> rooting of the phone, but with the programming, there are several
> configuration options in the phone itself that would assist identify
> tethering, vs. nontethering. There is the PPP Username and Password,
> the NAI, and the DUN NAI. Depending on the phone, how the carrier uses
> the programming (and profiles), and possibly other things, you can
> specify how each of those functions. So, if you hit the web, it uses
> the NAI. If you tether using USB which may present an ethernet
> interface to your laptop, it might use the DUN NAI. If the phone
> presents a simple modem via the USB interface, it might use the PPP
> Username and Password.
>
> So, how the connection is presented to your laptop is determined
> partially by the phone and what it is capable of, and partially by the
> programming. Again, I can't speak for rooted phones. But I'd guess
> that eventually you'd be found out - if the carrier has even a fairly
> unsophisticated system. If the average smartphone uses 4GB a month, and
> your phone magically uses 40GB, you'll show up on some list or another
> and end up getting a letter, a phone call, or simply no dialtone one day.
>
>
> Adam

The mobile interface, for what I see, is of course just an abstract framing system to a
mobile packet driver and hardware.

Apps use standard library IP socket interfaces and a simple addressable IP interface
(pointopoint or ethernet), standard IP stack, standard routing tables. When I tether it
simply routes packets and I can tcpdump everything on the mobile interface to verify that.
 Yes thats an oversimplistic view of the process however when I tether I don't see why
anything changes since the frame abstraction is in place and happy. If there are extra
hoops and ladders in CDMA land vs GSM land I will check them on my ACS phone when I have
time to find out - but that seems unlikely since you can use external C libs as well as
standard non Android SDK or IOS SDK functions to deal with raw sockets. Those would have
to be wrapped in a very complicated way in order to allow complete transparency.

I'd thought the PPP related credentials just helped set up the interface. The rest of it
helped identify the phone for other non IP related functions which apps can of course hook
in to, but don't provide a route to the Internet.

Looking for more info on this as a reply.

- Shane

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Received on Thu Jul 7 15:29:28 2011