Drones have created a new threat to people’s privacy. Anyone with a drone equipped with a video camera can potentially violate our privacy by streaming the subject in his/her private space over an encrypted first person view (FPV) channel.
Experts suggested many methods to detect nearby drones, but they all suffer from the same shortcoming: they cannot identify exactly what is being captured, and therefore they fail to distinguish between the legitimate use of a drone (for example, to use a drone to film a selfie from the air) and illegitimate use that invades someone’s privacy (when the same operator uses the drone to stream the view into the window of his neighbor’s apartment), a distinction that in some cases depends on the orientation of the drone’s video camera rather than on the drone’s location.
A group of Israeli researchers at Ben Gurion University in Beer Sheva (Ben Nassi, Raz Ben-Netanel, Adi Shamir, Yuval Elovici) have built a proof-of-concept system against surveillance operated with spying drones that is able to determine whether a certain person or object is under drone surveillance.
The system first generates a recognizable pattern on whatever subject someone might want to guard spy on with aerial surveillance, then researchers remotely intercept a drone’s radio signals and scan the streaming video the drone sends to the operator scanning for that pattern.
“In this paper, we shatter the commonly held belief that the use of encryption to secure an FPV channel prevents an interceptor from extracting the POI that is being streamed. We show methods that leverage physical stimuli to detect whether the drone’s camera is directed towards a target in real time.” wrote the researchers,
“We investigate the influence of changing pixels on the FPV channel (in a lab setup). Based on our observations we demonstrate how an interceptor can perform a side-channel attack to detect whether a target is being streamed by analyzing 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.”
The experts leverage the “delta frames” technique, instead of encoding video as a series of raw images, it’s compressed into a series of changes from the previous image in the video. A streaming video related to a still object contains fewer bytes of data compared with a streaming video of an object in motion or images that continuously change color.
That compression feature can reveal key information about the content of the video to someone who’s intercepting the streaming data, the technique works even when data is encrypted.
The Ben Gurion researchers used in the tests a “smart film” to toggle the opacity of several panes of a house’s windows. They used a DJI Mavic quadcopter to spy on the house, they demonstrated that the technique was able to detect the changing from opaque to transparent and back again of the panes. Then they used a parabolic antenna and a laptop to intercept the drone’s radio signals sent back to the operator and search the pattern in the encrypted data stream to detect if the UAV was used for aerial surveillance of the house.
“In another test, they put blinking LED lights on a test subject’s shirt, and then were able to pull out the binary code for “SOS” from an encrypted video focused on the person, showing that they could even potentially “watermark” a drone’s video feed to prove that it spied on a specific person or building.” reported Wired.
But Nassi confirmed that their technique works at ranges where it’s very difficult to spot a surveillance drone in the sky, the researchers tested their technique from a range of about 150 feet. The range is scalable by using a more powerful antenna.
Let me suggest reading the research paper.
(Security Affairs –drone surveillance, privacy)