Remote eavesdropping technique thanks to light bulb vibration

Observing the sound vibrations around light bulbs, the scientists demonstrate that the "lamphone" technique can eavesdrop from hundreds of meters away.

Eavesdropping techniques have evolved steadily over the years, from wiretapping by hacking phones, recording with hidden devices to using lasers to scan sounds. Recently, a new tool has been created to help spy activities become more sophisticated: Eavesdropping thanks to vibration analysis on the surface of the light bulb.

According to Wired, a team of researchers from Ben-Gurion University and the Weizmann Institute of Science, Israel has just introduced a new technique to eavesdrop on a word called "lamphone" .

This method uses a telescope and photoelectric sensor worth about $ 400. The device helps to observe the microscopic vibrations created by sound on the surface of the light bulb hundreds of meters away.

"This system helps to simulate all the sounds in the room, without hacking or using a third device in the room of the subject," said Ben Nassi, a security researcher at the University. Ben-Gurion said.

In the published experiment, the scientists placed a telescope lens about 25 meters away from the subject's room. They used the Thorlabs PDA100A2 photoelectric sensor to pick up signals from light bulbs in that room.

Electromagnetic sensor signals are converted to digital information by independent software developed by scientists themselves. This software can classify vibrations into different types of sounds such as basic noise, music and human voices.

In the eavesdropping experiment, the telescope lens and photoelectric sensor were located about 25m away from the target room. (Photo: Wired).

Through the telescope, the scientists collected vibrations of very small size, only a few hundred microns. After processing the signal through the software, they were able to reproduce room sounds with surprising accuracy.

For example, a speech of President Trump or the Beatles song "Let it be" can be separated between many of the room's noises.

However, this eavesdropping technique also has many limitations. In the experiment, the scientists used an uncoated ceiling light bulb. In fact, the lights are all placed inside plastic or glass enclosures, which can affect the frequency of the vibration being obtained.

The type of light bulb in the subject's room also significantly affects the listening results. LEDs produce 6.3 times more vibration with sound than incandescent bulbs and 70 times more than fluorescent bulbs.

In addition, if the subject in the room has a low voice, or deliberately whispered, speaking at a volume lower than normal, this wiretapping technique does not achieve the expected results.

From raw sound (Raw), the software has to go through 4 different steps to filter out noise and reproduce the room's sound. (Photo: Cyber ​​Security Labs).

The team said eavesdropping by analyzing light is not a new approach.

Previously, scientists have proven that laser beams can be used to illuminate a subject's room window to hear inside conversations. Or observing the vibrations of room objects like crusts and leaves can also help separate music and human voices.

"Lamphone solves the time problem, we immediately know what the subjects say just by the vibrations of light collected," Nassi explained the difference of the technique.

The group of scientists decided to publish this research not for espionage or law enforcement, but to demonstrate the miracles that science can do and to warn of privacy for everybody.

"We want to warn people about this new form of wiretapping, we are not engaged in the field of spying equipment , " Nassi said.