Surely if you have speakers at home, you have noticed that in many cases they include a small alert LED that tells us if the speaker is on or not. An LED that we now know can be a weapon that allows, with the appropriate means, know the audio coming out of the speakers.
Although it may not seem like it, such a tiny light is capable of generating a large amount of information and that is what a team of Israeli researchers has discovered at the time. analyze the flashing of the speaker LEDs. In this way they have been able to decipher the sound coming out of the speaker.
Much more than a warning LED
The team consisting of Ben Nassi, Yaron Pirutin, Tomer Cohen Galor, Yuval Elovici and Boris Zadov has been able to “hack” the speaker analyzing the flickering of the speaker LEDs. And it is that although it is imperceptible to the human eye, the small LED emits a series of flashes that are key in this discovery.
Based on these flashes, Ben Nassi and his companions, have managed to know what the speaker is playing. Therefore, these flashes serve to know a lot of information and do not remain just a simple warning system.
The basis of the experiment is that speaker flickers are related to the rise and fall of the electromagnet inside the speaker to create the vibrations that are responsible for generating the sound. Therefore, the increase or decrease in vibrations is related to reducing or increasing the intensity of the LED brightness.
For the experiment have used an electroscopic sensor capable of registering those blinks, which, as we say, are not perceptible to the human eye. With these changes in the LED registered, it is a matter of analyzing and deciphering the flashes, relating these changes in light to an increase or decrease in speaker vibrations. It is only necessary from there to decode the wave signal in audio.
According to the researchers, with this system they have achieved successfully capture and decipher sounds played on speakers at distances of up to 35 meters. All they have needed is to be able to clearly and clearly observe the brightness of the speaker’s LED and although the result is not perfect, it does offer quite a few clues about the audio coming out of the speaker.
And seeing therefore that even a simple LED on the speaker can be a “sneak”, the question remains as to how we can protect ourselves. We have no choice but to resort to the same system as with webcams and cover the LED so that no device can analyze the flickers.
Although it may seem something new, it is not something new for these researchers, since they already managed to analyze the brightness of a light bulb a year ago in a room with a telescope tens of meters away to decipher the conversation from the data collected. The method was called “lamphone” and it was dribbled in that music or any other sound produced vibrations on surrounding objects.
Via | Hackday
More information | Ben nassi