Smartphone shadows: Can information leak from walls and desks!?

When it comes to protecting your smartphone, the first things that come to mind are passcodes, fingerprint authentication, and encryption.

But would you laugh if I said, "Information can leak even from walls and desks"?
Unfortunately, this is not an urban legend but a topic actually researched in reality.

Here, the "shadow" does not mean a shadow of light, but the "vibrations" and "subtle sounds" emitted by the smartphone.
For example, when you operate your smartphone on a desk, the vibrations from your taps and swipes are transmitted to the surroundings through the desk.

Researchers capture these vibrations with special microphones and laser sensors

and have succeeded in estimating the positions pressed on the screen and the characters entered.

Furthermore, you cannot let your guard down even with walls.

The voice during a call is transmitted not only through the air from the speaker but also through walls and floors.
Using ultra-sensitive microphones and optical sensors, it is possible to analyze the subtle vibrations of walls from a distance and reconstruct the conversation content.

It sounds like a spy movie, but this method has actually been demonstrated at MIT and several universities.

So, what about more familiar risks?

For example, the moment you place your smartphone on a desk in a cafe or coworking space and enter your passcode.
If a sensor or modified device nearby records the vibration patterns of the desk...
The numbers or pattern lock traces you entered can be guessed before they are encrypted.

Of course, not everyone encounters this type of attack in daily life.

However,

for people with high information value such as political activists, executives, and journalists, it is a sufficiently realistic risk.

And as technology advances, the spy movie-level stories of today may become something ordinary hackers can imitate in the future.

As countermeasures,

・Hold your smartphone in your hand when entering input

・Avoid important operations while directly touching desks or walls

・Conduct confidential calls in physically isolated places

and so on.

If you are an AntiSpyPhone user, you can take prevention a step further.
There are settings to automatically turn off the accelerometer and microphone permissions only during input, and physical microphone blocking during calls, which can significantly reduce the risk of leakage via such "shadows."

Walls and desks should originally be allies, but in the world of information security, they can sometimes become "informants."

Next time you place your smartphone on a desk, it might not be a bad idea to doubt just a little, "Is this desk really not an enemy...?"