Long Distance Listening Devices

„Close the door, please!” Notoriously known sentence that cries for a bit of privacy. But does it help? Even with the door closed, interception isn’t out of question. Your office can be “bugproof”, but still, someone can be listening a few dozen meters away.

How do long distance listening devices work

When people talk, they create sound waves that spread in the air around them. When this wave hits window glass, it creates very small vibrations that are invisible to the human eye. However, they can be “visible” to a laser beam.

Laser interception uses simple physical laws – laser beam reflected from the glass panel of a closed window transmits vibrations of sounds in the room. Afterwards it is possible to reconstruct the original sound waves. It may sound difficult, but even on YouTube can be found easy demonstrations of this process in ideal conditions, even with devices for a few bucks.

Devices for long distance listening

A device for long distance listening can be constructed even by an amateur, using only a few trivial components.

The attacker is therefore only going to need a few primitive components (see above) to construct a device that will enable him/her to reconstruct conversations happening in buildings dozens of meters away.

Of course, the reality is much more complicated, and we need to work with occurring problems.

In the article about bug jammers you can find out more about the possible protection from laser interception. That an installation and finding of the right angle for a laser interception isn’t easy, knew even the CIA in 1960, when its agents targeted the Russian embassy.