Beware – any light bulb in a room that is visible from the window can be utilized for spying on your conversations from afar. The discovery comes from a team of researchers at the Ben-Gurion University of the Negev in Israel. The team has found that the patterns of vibrations in a light bulb can allow us to recover full conversations from a distance of hundreds of feet away.
How is that possible, you ask? It is possible because a hanging light bulb not only acts as a diaphragm but also a transducer. This makes it a viable gadget for any intruders who might want to eavesdrop on your conversation. The paper says, ‘We show how fluctuations in the air pressure on the surface of the hanging bulb (in response to sound), which cause the bulb to vibrate very slightly (a millidegree vibration), can be exploited by eavesdroppers to recover speech and singing, passively, externally, and in real-time.’
The technique has been named ‘lamphone’ and can be executed by having a laptop, telescope, microphone, and remote electro-optical sensor for under $1,000 as per the research team. The team tested the method by setting up the equipment on a pedestrian bridge about 80 feet away from a third-floor office located inside a commercial building.
Using a 12-Watt LED light bulb, the team was able to not only monitor one sentence but two songs that were played via speakers in the office. The team further notes that the range could be amplified, given that you have the right kind of gear at your disposal.
There are, however, some exceptions to this. The paper says that the hacker must have a clean line of sight between their electro-optical sensor telescope and the hanging light bulb. This implies that the technique is useless if there are lampshades involved or if there are curtains. Other factors also include the thickness of the light bulb and the output of light and how close the people are to it.