[guardian-dev] signal without sim ?
rz at linux-m68k.org
Wed Jan 15 16:02:48 EST 2014
On Mon, Jan 13, 2014 at 03:53:18PM +0100, Timur Mehrvarz wrote:
> > the only reliable way to detect this is monitoring power draw and RF
> > transmission (SDR) via external systems. this has been in the threat
> > model for high value targets many years now...
> Instead of turning all radios off, airplane mode *could* switch cellular
> to some very low-power pure listening mode. Power draw would be so low,
> you would get the impression, that cellular has actually been turned
> off. But the device would allow full cellular to be re-activated
> remotely via some GSM command.
the key here is GSM because listening on any kind of 3G network would
require somewhat noticeable power consumption. It is not only the radio
HW but also some CPU power that is involved. With GSM only the power
consumption can be indeed extremely small.
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