Ask Hackaday: How Do You Detect Hidden Cameras?

The BBC recently published an exposé revealing that some Chinese subscription sites charge for access to their network of hundreds of hidden cameras in hotel rooms. Of course, this is presumably without the consent of the hotel management and probably isn’t specifically a problem in China. After all, cameras can now be very tiny, so it is extremely easy to rent a hotel room or a vacation rental and bug it. This is illegal, China has laws against spy cameras, and hotels are required to check for them, the BBC notes. However, there is a problem: At least one camera found didn’t show up on conventional camera detectors. So we wanted to ask you, Hackaday: How do you detect hidden cameras?

How it Works

Commercial detectors typically use one of two techniques. It is easy to scan for RF signals, and if the camera is emitting WiFi or another frequency you expect cameras to use, that works. But it also misses plenty. A camera might be hardwired, for example. Or store data on an SD card for later. If you have a camera that transmits on a strange frequency, you won’t find it. Or you could hide the camera near something else that transmits. So if your scanner shows a lot of RF around a WiFi router, you won’t be able to figure out that it is actually the router and a small camera.

Fire alarm? Camera? It is both!
The other common method uses a beam of light or a laser to try to see reflections of lenses, which will be retroreflective. The user views the room through a viewfinder, and any light that comes directly back will show up in the view. Despite some false positives, this method will find cameras even if they are not powered or transmitting. Even shining a flashlight, maybe from the same cell phone, around a dark room might uncover some camera devices.

There are a few other techniques. If you assume a spy camera probably uses IR lighting to see you at night, you can scan for that. A good tip is that your cell phone camera can probably see IR. (Test it on an IR remote control.) So looking around with your phone camera is a good, free way to find some cameras. A thermal imager might show hidden equipment, too, although it might be hard to determine if it is actually a camera or not.

You might be thinking: just look for the camera. But that’s not always simple. In the BBC article, the camera was the size of a pencil eraser. Not to mention, a quick search of your favorite retailer will reveal cameras made to look like smoke detectors, stuffed toys, USB chargers, and more. You can even get small cameras that can mount a fake button or screw head on the lens.

Testing

[Project Farm] has a video that tests a few detectors. The problem, of course, is that there are different kinds of cameras. Detecting the test camera doesn’t mean it will detect all cameras. Still, you can get some idea of how effective some detectors are compared to others.

youtube.com/embed/1reman2waLs?…

Your Turn?

Given that none of the current ways to detect cameras work perfectly, what would you build to find them? Maybe an NLJD? Or maybe some tech to blind them? Tell us what you think in the comments.

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