3dr solo teaser 648 - Drone perves defeated by tinfoil houses

Drone perves defeated by tinfoil houses

Boffins figure out when drones are watching, without decrypting the video stream

Even then, detection turns out to be pretty straightforward: as researchers from Ben-Gurion University of the Negev and the Weizmann Institute of Science explain, you don’t need to decrypt the stream at all, you just need to apply a stimulus you control.

Their approach, revealed here and published in detail at arXiv, detects how video bitrate changes given a particular stimulus.

In other words, it’s a particular kind of side-channel attack – which is no surprise, since the researchers in question have applied their skills to side-channel attacks for years.

In the new paper they write: “we demonstrate how an interceptor can perform a side-channel attack to detect whether a target is being streamed by analysing the encrypted FPV channel that is transmitted from a real drone (DJI Mavic) in two use cases: when the target is a private house and when the target is a subject.”

Researcher Ben Nassi, a student of BGU professor Yuval Elovici, said: “The beauty of this research is that someone using only a laptop and an object that flickers can detect if someone is using a drone to spy on them … While it has been possible to detect a drone, now someone can also tell if it is recording a video of your location or something else”.

As demonstrated in the video below, the interception takes advantage of how video encoding algorithms work: if nothing changes in an image between frames, the codec doesn’t need to re-sent redundant information.

Youtube Video

If someone’s using a drone to snoop – in the video the drone operator’s observing a house – they’ll park the drone and aim it at the target for a while. Because that image is relatively stable, compression will settle the bitrate the drone transmits down to a fairly low level.

The stimulus the researchers applied was via a “smart film” on the windows, but opening and closing shutters would do just as well: in response to the stimulus provided by the snart film, the bitrate rises, and an interceptor with a suitable RF scanner can see that change without decrypting the video stream.

The researchers also tested whether the technique could be used against drone surveillance over individuals: “In a second outdoor test, researchers demonstrate how an LED strip attached to a person wearing a white shirt can be used to detect targeted drone activity. When researchers flickered the LED lights on the cyber-shirt, it caused the FPV channel to send an ‘SOS’ by modulating changes in data sent by the flickering lights.” ®


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