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(Apologies if the answers to the following questions seem obvious, but I am not an expert, so thought I'd ask.)

The larger question can be broken down, but I don't believe the subquestions are worthy of separate SE questions, so here goes:

1. True or false: when one puts any Android device in airplane mode, one disables all signal transmission from the device.

I believe the answer to this is true, but would be interested to know of, e.g. (in descending order of interest),

  • the extent to which this statement is not true for all Androids OOTB. E.g., are there specific makes/models for which this statement is not true?
  • the extent to which one or more Android devices can have airplane mode turned off by an external signal. Example scenario which comes to (my paranoid :-) mind:
    • could a private anti-theft service, presumably with matching app, ping a device such its app takes the device out of airplane mode to respond?
    • do any governments require devices purchased in their jurisdiction require to respond to some external signal?

2. True or false: any Android device which cannot transmit signals cannot be geotracked.

Again, I suspect this to be true, but would be interested to know about non-trivial ways in which it might be false. An example of a non-trivial defeat would be a device that has a factory-installed passive RFID tag. An example of a trivial defeat would be for a user to attach a GPS beacon to her/his device.

If both of those are true, then one cannot (trivially) geotrack the location of an Android device in airplane mode ... unless I'm missing something ...

2

Answer to both is: "Depends".

Airplane mode

What is that nowadays, where air planes allow you to use WiFi and Bluetooth? Don't say this is an unrelated question in this context. Not only does the term originate there, but it can be as variable as how each airline deals with it:

$ adb shell settings get global airplane_mode_radios
cell,nfc,wimax,bluetooth,wifi
$ adb shell settings put global airplane_mode_radios "cell,nfc,wimax"
$ adb shell settings get global airplane_mode_radios
cell,nfc,wimax

What's that? The first is what you probably expected: all kind of signals are toggled by airplane mode (line 2). But it can be changed (line 3), and then looks very different (line 5). I've e.g. excluded WiFi on some of my devices. Different manufacturers/ROMs might have different presets. So there can't be a general answer unless you define "airplane mode". And of course there are apps that can automatically toggle all that (at least on rooted devices) – your "anti-theft" guess is a very good example for that. A paranoid person could even use e.g. to configure a "watchdog": "Whenever my device leaves a configured geofence, automatically report its location to my server in 30s intervals. If needed, enable WiFi or mobile data for that." Might be complex, but doable. On non-rooted devices, that's limited though – not at last by:

$ adb shell settings get global airplane_mode_toggleable_radios
bluetooth,wifi,nfc

Again only an example, which might not be valid for each and every device (concerning line 2). You might already have guessed it:

adb shell settings put global airplane_mode_toggleable_radios "bluetooth,wifi,nfc,wimax,cell"

And with that, everything can be toggled again. According to a test performed by Prahlad Yeri, this even works on non-rooted devices. Settings applied this way survive a reboot (but of course not a ).

Any Android device which cannot transmit signals cannot be geotracked

Without some paranoia, I'd give a "yes" to that – though to be exact, the condition is hard to meet: as soon as it's powered up, it will emmit some "signature" which one could track – but that would need quite expensive equipment, and the range would be quite limited :)

If in this context you speak of an "attached GPS beacon": well, you could track a cake that way, or a cat, your cigarette box, or a brick for that – it no longer has anything to do with the device itself. Almost everything can be "bugged".

  • @izzy: 'you speak of an "attached GPS beacon": well, you could track a cake that way' ... which is why I referred to that as a 'trivial defeat' while asking for 'non-trivial' ones. – TomRoche Jul 16 '16 at 4:02
  • @TomRoche I must pass in that case. Not due to lack of phantasy – but due to lack of what's done in reality. Which is why I wrote "without some paranoia". Many things are technically possible – but that doesn't make them feasible. Though I'm willing to believe that some of our current "surveillance states" would like measures to be implemented by-default, it's doubtful they can really force this for "mass production" (especially in countries they cannot control – like the US for Chinese/Korean devices). And manipulating all devices on import is … paranoia? ;) – Izzy Jul 16 '16 at 11:01
  • @Izzy - Thanks for the info! I recently ended up ALMOST hard-bricking my Xiaomi MiPad by a wrong-click on the SuperSU app, so I want to understand the Android world more first before I try to root this device. However, I've found that MediaTek devices are pretty easy to root without any danger of hard-bricking. – Prahlad Yeri Jul 16 '16 at 11:02
  • @PrahladYeri as you have a non-rooted device (obviously), why not try the above and report back? I'd update my answer then accordingly, and we could cleanup corresponding comments. – Izzy Jul 16 '16 at 11:04
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    @Izzy Yes, I can confirm that setting the airplane_mode_radios works from a non-rooted phone too (tested on the MiPad running KiKat) and even survives the reboot! – Prahlad Yeri Jul 16 '16 at 11:11

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