Lamphone: listen to conversations via a light bulb

Lamphone: listen to conversations via a light bulb Cybersecurity

In a research article published this week, academics presented in detail a new method of retrieving conversations and audio recordings by observing the vibrations of a light bulb.

This technique, which they called Lamphone, is based on the principle that objects vibrate when the sound wave hits their surface.

When this happens in a light bulb, academics claim that vibrations also create small flickers in light emissions. They claim that by using powerful sensors, they can record variations in light and reverse the sound waves hitting the surface of the bulb.

But like any new surveillance technique, Lamphone has its advantages and limits.

The most obvious is that attackers need a line of sight to the light bulb in a room or public space. Bulbs protected by lampshades are immune to this attack, as are conversations that take place in windowless rooms.

However, once he has a line of sight on a bulb, academics claim that an attacker can use tools like a telescope and an electro-optical sensor to record variations in the light in the bulb. This capture is possible from a distance and does not require being close to the target.

In experiments carried out for their research, they declared that they had succeeded in recovering sounds and conversations at a distance of 25 meters.

“This range can be amplified with appropriate equipment (larger telescope, 24/32 bit ADC, etc.),” ​​said the research team.


In their experiment, the research team reported having successfully recovered both human speech and room effects, such as music played in the background (see the demo below for an example).

The downside is that the conversations have to be loud enough to generate vibrations, or the speakers have to be close enough to the bulb.

However, being able to listen to desktops from tens of meters away with nothing more than a telescope and video recorder is a huge feat, and a dangerous scenario for many businesses.

But Lamphone is not the first attack of its kind. Other techniques have been explored in the past, such as Gyrophone (using sensors from mobile devices to recover speech from gyroscope signals) and Visual microphone (using video recordings to recover passive sound).

Nevertheless, the research team claims that Lamphone has an advantage over these attacks because it is passive and does not require infecting the victim’s device with malicious software (unlike Gyrophone). This attack also works in real time and does not require access to vast computer resources to process its recorded data (unlike Visual Microphone).

The research team claims that all that an attacker needs to process Lamphone data is a laptop.

However, the attack does not work against all types of bulbs and the results may vary depending on the brand, model and technical characteristics of the bulb, such as the thickness of the outer glass or the emission capacity. from light.

Additional details are available in the search article, titled “Lamphone: Real-Time Passive Sound Recovery from Light Bulb Vibrations“. PDF. The work of the research team will be presented in August at the Black Hat Security Conference.

Academics from the Ben-Gurion University of the Negev and the Weizmann Institute of Science contributed to this work.

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