Sensing the sensors

How many sensors does your smartphone have? One? Two? Three? The Samsung Galaxy Note 20 Ultra 5G (yeah that's one phone!) has six sensors and that's excluding the fingerprint sensor, camera(s) and microphone(s). It might not occur to you but these sensors are powerful enough to allow some kind of surveillance. To demonstrate, there's this cool android application called PrivacyBreacher.

PrivacyBreacherPrivacyBreacher's 3D render from smartphone sensors

Yes, I know, that's just a cube rotating but the cube is rotating according to the orientation of my smartphone. This can actually be very well used to construct a virtual model of the surroundings of the mobile device. Don't believe me? Google already has an actual application for this. It is called “Find My Device”, it can construct 3D surroundings of your phone. How? By using these sensors, just how PrivacyBreacher does. Now combine these sensors with camera and microphone and voila! you have a perfect surveillance device. You can install PrivacyBreacher which shows more information about various activities on your smartphone that can be tracked. You can also check out the article, if you are into the technical stuff. Did I forget to tell you the best part? Access to all these sensors does not need any permission!

What are the solutions?

You might think that not much can be done about these sensors but that's not true. Some steps can be done to get a sense of these sensors. Here are the possible solutions:

Sensors off mode

If you are on Android 10 or higher, I may have a solution. It is called the Sensors off mode, it can be added to the notification shade. It will work as a toggle for most of the sensors on the smartphone. Note that microphone is a hit or miss with some applications. On my smartphone, the dialer application works just fine even with sensors off but other applications like WhatsApp or Telegram were not able to access the sensors. Even the Camera application on my device can't access the sensors. Your mileage may vary depending upon your smartphone's software. This is not as good as a physical kill switch but it is the best we have got.

Here's how you can enable Sensors off tile:

  1. Enable developer options. The process varies depending upon your device, you should be able to duck (yeah no Google here) it!
  2. Go to “Developer options”.
  3. Select “Quick settings developer tiles” option in the menu.
  4. Enable “Sensors off” toggle.
  5. You should be able to find the Sensors off tile in the edit section of your notification shade. Just pull it to the active region.

Sadly, for android users who are running Android 9 or lower, there's nothing much that can be done about these sensors that don't require permissions. But you can do something about the more sensitive sensors, so read on.

Camera and microphone

These are the most sensitive sensors on your smartphones. That's why Android requires users to explicitly grant the permission to access these sensors but most people grant these permissions without reading or thinking. Kudos to Apple, they added these amazing indicators for camera and microphone in their latest software upgrade:

iOS 14 privacy indicatorsCamera indicator on iOS 14

When there's Android, there is a way. The Android developers' community has proved this saying again. Cometh Privacy Indicators, it does exactly what Apple's iOS does, show you an indicator whenever an application uses your device's camera or microphone. Here's a demonstration:

Privacy IndicatorsPrivacy Indicators' demo

You can get Privacy Indicators on the Google Play Store or the IzzyOnDroid F-droid Repository. Do note that the application only shows indicator for the main camera sensor. (I have created an issue about this, do contribute if you know any workaround.)

Still not satisfied?

If you feel this is not enough for your threat model, you can check out PinePhone by Pine64. This phone is powered by GNU/Linux and has actual kill switches for various sensors on the device:

Kill switches on the back of PinePhonePhysical kill switches on PinePhone (Image from Android Police)


Well, that was all about sensors on your smartphone. Stay tuned for more fun articles. You can always reach out to me by visiting this page.

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