The downside of using a faraday cage with an activated phone: The phone will start "screaming" looking for a tower, and you'll get much reduced battery life. Turning phone off first and *then* putting it in the bag saves battery and prevents any suspected "backup battery" driven chips from getting a signal out..although if that's your threat-model, they could just record whatever telemetry they need and send later. i.e., if a phone is suspected to be compromised and could turn on the core or auxiliary chips (with main or backup battery), and activate the microphone or camera, the faraday cage bag will prevent it from sending that data right away but it could be instructed to store that data instead and send it back later. Personally I think removing the battery is sufficient for most phone models; the backup batteries are unlikely to be enough to drive the more concerning chips and sensors for long even if they're wired up to it in the first place. On 03/05/15 19:45, Mirimir wrote:
On 05/03/2015 11:20 AM, Georgi Guninski wrote:
On Sat, May 02, 2015 at 06:21:16PM -0600, Mirimir wrote:
For the Faraday bag, see <http://www.instructables.com/id/RFID-Secure-Wallet/>. It's easy to test. Just put the phone in the bag, and call it. If it rings, there are leaks.
I am noob at smartphones, but isn't this very close to functionally equivalent to just physically remove the battery from the phone?
At what distance is phone with removed battery detectable?
Well, if someone implanted "backup battery" this fails, but the implanted battery must be sufficiently small to not see it.
I don't know enough about smartphones to say. The effectiveness of removing the battery may vary among devices. Snowden told people visiting him in Hong Kong to put their phones in the refrigerator, which is a Faraday cage. Also, using a bag is arguably less hassle than removing the battery.
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