Original paper: https://arxiv.org/pdf/1801.03074.pdf
A proof-of-concept system for counter-surveillance against spy drones
21–30 of 71 posts
Re: A proof-of-concept system for counter-surveillance against spy drones
#22This defense is plausible for fixed frequency broadcast video feeds. Likely as drone usage grows and becomes ever more sophisticated (say nothing of current 'nation state grade' systems), their video feeds will likely be spread spectrum and highly directional (if nothing else, directional transmission makes the drone's video feed far more power efficient), making intercept and this type of analysis difficult.
Re: A proof-of-concept system for counter-surveillance against spy drones
#23>In other words, they can see what the drone sees, pulling out their recognizable pattern from the radio signal, even without breaking the drone's encrypted video. The most interesting part of this is how encrypted traffic leaks enough info to be reliably analyzed. Really cool stuff.
Seems like you could also hijack their signal to use for your own communications. By affecting the frequency and intensity of the variations you can create a binary or analog signal that rides on top.
Re: A proof-of-concept system for counter-surveillance against spy drones
#24My tl;dr understanding: Drones send video back to operator. Video is typically compressed so that it only updates part of the picture that have changed. Even if the video is encrypted, the researchers are able to measure the bitrate. Thus when the researchers make a significant change like putting a board against a window, and seeing if the traffic increases, the researchers can determine whether the drone is looking…
I'm assuming this is predicated on the drone being absolutely still and that nothing in the scene (leaves on trees) is moving? Is that even realistic?
Generally speaking, inter-frame video compression uses an amount of data directly related to the amount that things change from one frame to the next. So while noise like leaves moving shows up as small changes moment to moment, larger changes are still realistically visible.
My younger years spent screwing around with video for a hobby are coming back to me now.
Re: A proof-of-concept system for counter-surveillance against spy drones
#25My tl;dr understanding: Drones send video back to operator. Video is typically compressed so that it only updates part of the picture that have changed. Even if the video is encrypted, the researchers are able to measure the bitrate. Thus when the researchers make a significant change like putting a board against a window, and seeing if the traffic increases, the researchers can determine whether the drone is looking…
I'm assuming this is predicated on the drone being absolutely still and that nothing in the scene (leaves on trees) is moving? Is that even realistic?
Shouldn't simple linear movement of a scene still compress really well?
Re: A proof-of-concept system for counter-surveillance against spy drones
#26And that is why drones will start landing on tree branches and the poles of street lamps. And why they'll start using cell networks.
Re: A proof-of-concept system for counter-surveillance against spy drones
#27I expect image detection in a video stream is pretty advanced these days but I'd imagine you'd need to rotate the image being recorded 3D space to match the plane of the window so you can compare them both? If you know the position of the drone relative to the window, that's doable. Maybe the algorithms are clever enough to account for that these days.
Interesting article - thanks for sharing.
Re: A proof-of-concept system for counter-surveillance against spy drones
#28My tl;dr understanding: Drones send video back to operator. Video is typically compressed so that it only updates part of the picture that have changed. Even if the video is encrypted, the researchers are able to measure the bitrate. Thus when the researchers make a significant change like putting a board against a window, and seeing if the traffic increases, the researchers can determine whether the drone is looking…
Couldn't this be bypassed by regulating a drone's bitrate to a constant steady flow? The sacrifice will be either video quality or freshness of data, but it would be a straightforward way get past that protection.
Re: A proof-of-concept system for counter-surveillance against spy drones
#29My tl;dr understanding: Drones send video back to operator. Video is typically compressed so that it only updates part of the picture that have changed. Even if the video is encrypted, the researchers are able to measure the bitrate. Thus when the researchers make a significant change like putting a board against a window, and seeing if the traffic increases, the researchers can determine whether the drone is looking…
I'm assuming this is predicated on the drone being absolutely still and that nothing in the scene (leaves on trees) is moving? Is that even realistic?
Well, It assumes that the amount of delta you can create in the transmitted image is sufficiently large that you can discern it from other sources of random variation in the image.
So if the drone is moving around dramatically and there are huge deltas in the image, making your windows opaque / translucent repeatedly may not be sufficient signal. But if the drone is observing a dark compound and you flash lights everywhere repeatedly, it might not matter that the drone is moving around a lot - there might still be a dramatic change in the data transmitted by the drone.
Ultimately you're putting some signal into a potentially noisy channel and trying to reconstruct whether or not your observations contain that signal. The example is simple enough that normal human eyeballs looking at the output can detect it. Using more sophisticated techniques might be able to tease out smaller signals from noisier channels.
Re: A proof-of-concept system for counter-surveillance against spy drones
#30My tl;dr understanding: Drones send video back to operator. Video is typically compressed so that it only updates part of the picture that have changed. Even if the video is encrypted, the researchers are able to measure the bitrate. Thus when the researchers make a significant change like putting a board against a window, and seeing if the traffic increases, the researchers can determine whether the drone is looking…
Couldn't this be bypassed by regulating a drone's bitrate to a constant steady flow? The sacrifice will be either video quality or freshness of data, but it would be a straightforward way get past that protection.
Yes, just like anything...but it comes with a trade off.