[guardian-dev] signal without sim ?

Hans-Christoph Steiner hans at guardianproject.info
Thu Jan 9 11:51:51 EST 2014



On 01/09/2014 11:36 AM, shmick at riseup.net wrote:
> 
> 
> Hans-Christoph Steiner:
>>
>> Airplane mode is implemented in software, so there is no guarantee that it is
>> actually turning off any radios.  This is the same case as the power buttons
>> on phones: they don't physically cut power to the device, so many devices
>> don't really turn off at all when you "turn them off".
> 
> can the lay person test this with off-the-shelf products ?
> can you recommend decent irc channels and/or mailing lists dedicated to
> mobile networks ?
> 
> thanks for answering albeit off-topic to list

This is definitely on-topic for this list!  We'd love to help you dig deeper
in this topic since its largely a big question mark.

We've had a bunch of questions about airplane mode.  To start with, is it
actually turning the GSM/CDMA/LTE radios off?  It is possible that the radios
are not turned off in airplane mode, but instead they are put into passive
listen mode, where they can listen to all signals coming in.  Then they could
respond if a certain signal was sent to them, like some kind of "every device
report your location" signal.

As for without a SIM, it is clear that the radios are still on even with a SIM
card.  What I don't know is whether some calling is still possible.  For
example, is it possible to dial the emergency number when there is no SIM card
in the device?

As for off-the-shelf equipment for tracking radio signals, there is a lot, but
its pretty expensive.  For example:
http://www.datalinkstore.com/signal-strength-analyser-p-217.html

For answering some of the questions about airplane mode, my guess is that a
raw signal analyzer is required, not a GSM one for example.  Then you could
run a test that just logs any transmission at all from the cellular radios
from a device in airplane mode, regardless of whether it is part of a standard
protocol like GSM, CDMA, LTE, etc.

.hc

> 
>>
>> NSA whistleblower mentioned in one interview that the interviewer's phone
>> could be controlled by the NSA, even if he "turned it off".  If you are
>> concerned, remove the battery.
>>
>> .hc
>>
>>
>> On 01/09/2014 10:57 AM, shmick at riseup.net wrote:
>>> how does the following make sense
>>>
>>> android phone *without* sim & aeroplane mode *on*
>>>
>>> network: unknown
>>> signal strength: -51dBm
>>> mobile network type: UNKNOWN:0
>>> service state: radio off
>>>
>>> android phone *without* sim & aeroplane mode *off*
>>>
>>> network: unknown
>>> signal strength: -81dBm (fluctuating strength; stationary phone)
>>> mobile network type: EDGE:2
>>> service state: out of service
>>>
>>> i thought in aeroplane mode all radios were off and you could, depending
>>> on the phone, enable wifi, bluetooth selectively, etc
>>>
>>> but where is the signal strength coming from - i thought a phone could
>>> not associate/ping a cell tower without a sim *unless* making an
>>> emergency call
>>>
>>> also why does a phone without a sim last immensely longer (in my case)
>>> than compared with aeroplane mode with a sim ?
>>>
>>> can/do phones ping/associate cell towers/base stations in aeroplane mode ?
>>>
>>> can/do phones ping/associate cell towers/base stations without a sim ?
>>>
>>> (probably, if your phone is ownd anything is likely)
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>>
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