Israeli scientists have found a way to listen to what someone is saying in a room more than 80 ft away - by pointing a telescope at a lightbulb.
Ben Nassi, a security researcher at Ben-Gurion University, led the study into the spyware, which requires a laptop and equipment costing under £1000.
The new invention has been called the "lamphone".
After a lightbulb is touched by soundwaves, the surface vibrates and the resulting light emissions are picked up by sensors.
The flickers of light are measured and converted into an electric signal, allowing scientists to pick up sound that can be transcribed into conversation.
Mr Nassi told Wired Magazine: "Any sound in the room can be recovered with no requirement to hack anything and no device in the room.
‘’You just need line of sight to a hanging bulb.’’
Mr Nassi – who developed the lamphone with Yaron Pirutin and Boris Zadov – said they had been attempting to look into ways in which organisations could protect themselves from spies.
The research group, who included the scientists from the Weizmann Institute of Science, were surprised to find they could recognise The Beatles' Let It Be and a speech by President Trump from a room 82 ft (25m) away.
They discovered that the technique failed to work when lightbulbs were embedded in the ceiling or mounted onto a fixed lamp.