Show HN: RF Hunter – Find hidden cameras and other devices
github.comThis project is an RF Signal Scanner built using an ESP32, AD8317 RF detector, and various other components. It's designed to detect and measure RF signals in the environment and display the signal strength on an OLED display. It's useful to find hidden cameras, wiretapping devices, and other RF-enabled devices.
Fun fact, you can actually detect semiconductor devices even if they are powered off and hence emit no radiation unless the design took specific precautions. This works by illuminating a region with high frequency electromagnetic radiation and then listening for the effects that PN junctions have on the reflected radiation due to their nonlinearity. [1]
[1] https://en.wikipedia.org/wiki/Nonlinear_junction_detector
> Thousands of diodes were mixed by the Soviets into the building's structural concrete, making detection and removal of the true listening devices by its American occupants nearly impossible.
Wow ...
Yeah!
It also makes me suspect that the device would not be super-useful in most environments today because our homes and offices have false positives littered all over the place. Such a countermeasure would be unnecessary now.
That's called playing the long game, and playing it quite cleverly!
Very cool! Could this work for detecting nearby drones?
2018, "Low budget consumer hardware espionage implant", 220 comments, https://news.ycombinator.com/item?id=40363704 & https://news.ycombinator.com/item?id=20190251 & https://news.ycombinator.com/item?id=15676737
2019, "Airbnb Has a Hidden-Camera Problem", 50 comments, https://news.ycombinator.com/item?id=24324300
2019, "How to find hidden cameras in your AirBnB", 300 comments, https://news.ycombinator.com/item?id=20457419
2023 repro of "Great Seal Bug" (1952): mechanical microphone, no power source, data exfiltrated via external directed microwave beam, https://www.youtube.com/watch?v=NLDpWrwijE8
Try measuring the RF emissions of:
Thanks for making this public. What's the ballpark BOM cost?
Could a directional antenna help with locating RF sources? There's some older work ("WokFi") on parabolic antennas for WiFi, https://web.archive.org/web/20140802123553/http://www.usbwif...
Here's another circuit design for AD8317, https://g8rwg.uk/articles/noise-meter-ad8317/
> The AD8317 module I’m using has the logarithmic slope set to 22mV/dB. I used the output of a Viavi JD785 at different frequencies to check the slope and dynamic range of the device. Linearity and dynamic range at 1GHz and 3.5GHz is good and as expected drops off at 144MHz and 6GHz.
> What's the ballpark BOM cost?
https://github.com/RamboRogers/rfhunter/blob/master/rfhunter... contains amazon links. About $100 although many of the required components come as packs.
The most effective way would be use a Thermal Camera, because a normal "hidden camera" you get from eBay will consume around 5 Watts - a significant heat dissipation.
For others, probably just get an off the shelf TinySA?
Another way to detect hidden cameras is optical augmentation, using reflections to locate lenses; this can detect cameras that aren't currently on / actively transmitting.
Some paper and product references:
- (PDF) http://s3.amazonaws.com/arena-attachments/1381379/c3a4e75132...
- https://www.spycatcheronline.co.uk/product/camera-detector/
- https://www.ijser.org/paper/Lens-Detection-System-using-Opti...
- https://patents.google.com/patent/US20090237668A1/en
> TinySA
What's the frequency range and scanning speed of TinySA?
This is cool. Is is all point-to-point wired inside? I can't imagine a PCB design would be too difficult if all the RF stuff is handled by the IC.
yeah, it's just soldered up to the pins. More details here: https://blog.matthewrogers.org/b/8BCF175A-6CC6-4E61-8310-A91...
Does anyone have a personal experience with finding a hidden camera in an AirBnB?
Well, not in an AirBnB, but... Already years ago, they found one in the ladies room at work...
A way easier solution to this is to turn off all of the lights and look around with your phone camera.
The phone camera will pick up the bright IR lights that hidden cameras use to illuminate the room-- wireless or not.
Obviously this only works if the camera uses IR lights, but pretty much all of the sneaky ones do.
Most phone cameras have pretty steep IR cut filters these days. The front camera on most phones still don't, so you have to use that.
That said, most of these spy cameras don't have IR illuminators...
do you have examples of cameras or smartphone which do not have IR filters?
I don't but it's easy to test, just pick up a TV remote and press a button while pointing it towards the camera. It should look like a flashing white LED.
I should also mention that both IR illuminators and TV remotes are usually either 850nm or 940nm, I have not looked into that aspect of it. I imagine that it's possible that your camera can detect one but not the other...
Thanks, I had no idea about this.
My Google Pixel 8a doesn't show anything on either camera, but my friend's front camera did! It shows up light purple.
My phone goes up to 980nm and it is a Note 9.
Both front and rear cameras work.
The light shows up as a pinkish purple.
Raspberry Pi sells a camera especially without IR filter.
Most of the bright IR lights you find on typical surveillance cameras actually visibly look a little red. I wouldn't think the same lights would be used if the intention is to spy in secret.
Well, maybe - it would need to have ir enabled. This also detects listening devices etc.
Would this also be able to detect something like a camera that saves videos to an SD card to be retrieved later? Something that doesn't use WiFi or a radio?
That's the main limit I see, but I'm wasn't sure if it such a device would still generate enough RF intrinsically w/o a radio.
Maybe those could be found with a parabolic antenna and possibly an amp, ideally one with a limited range one can control via software.
Once a few common signals are known, the software could do programmed patterns to ferret out easy ones.
I have long dreamt about building a portable phased array for this purpose, but additionally using the phase difference between receivers to visualize where the transmission source is.
In effect a camera into the RF world!
Could be combined with AR, https://hackaday.com/2019/01/09/smartphone-app-uses-ar-to-vi...
DIY radio telescope tuned to 2.4Ghz WiFi, https://www.youtube.com/watch?v=g3LT_b6K0Mc
Image of physical building overlaid with RF sources, https://www.facebook.com/thethoughtemporium/posts/2162600763...
> When I made the first video and photoshoped my impression of what I thought this would look like, I never imagined it would actually be this close. It's official, our telescope can map the wifi in a building as if it were any other form of light.
Those 128x64 displays are easy to use, but frustratingly variable. They have differing start up sequences which using the wrong one leaves a blank screen.
> They have differing start up sequences which using the wrong one leaves a blank screen.
You mean, bricked?
OP, cool project. I have questions though:
How does the device detect very short bursts? After looking up the data sheet of the RF detector I believe you would need additional circuitry to not risk that very short bursts slip through the sampling of the ESP A/D input.
Second, the supply voltage of the detector seems to be 3.0 V to 5.5 V, https://www.analog.com/en/products/ad8317.html
Title is misleading. It only detects RF. A hidden camera could record to storage for later upload in which case wouldn’t be transmitting continuously.
Depends on the sensitivity of the device. It might be possible to pickup the EMF of the camera, even if it's not actively broadcasting.
Every current carrying trace is an antenna.
What you really need is a Non-Linear Junction Detector. These can detect an unshielded device with transistors, even if it's off.
https://en.wikipedia.org/wiki/Nonlinear_junction_detector
That would only be practically useful in an environment devoid of all other electronics. How would one tell between the non-transmitting spy cam and normal household electronics
By having some spatial/angular resolution. You'd need a large directional antenna or multiple antennas to have something similar to a phased array radar, but passively (i.e. listening only).
In Japan there was a requirement to make a noise when taking a picture on a phone. I'm not a huge fan of that since there are a lot of reasonable reasons to not want noise, but I would be a fan if any capture device was require to advertise its presence wirelessly to make it easy for any smart device to notice an active recording device nearby. That wouldn't stop sophisticated surveillance but it would act like a cheap lock and stop a lot of the abusive stuff, or at least let people more quickly notice it.
Of course nefarious actors will ignore the requirement and or hack their gear.
There is an upside though. An additional criminal charge, and making it easier to prove intent.
(Note I said easier, not just "prove", for it is indeed only easier.)
> but I would be a fan if any capture device was require to advertise its presence wirelessly to make it easy for any smart device to notice an active recording device nearby
That would be convenient for burglars or dishonest cops.
Dang. Never thought of that. No free lunch, eh?
This Device lights up pretty good on wireless or cellular data transfer. If my wife starts browsing on her phone it lights up.
What is the sensitivity/range? I've always wanted something like this to carry in the woods to detect game/trail cameras. Not for any nefarious purpose, but to get an idea of how surveilled the woods are.
Don’t many of those just store data locally?
Yes but since it's the woods and not a university computer lab the only other noise source should be your personal devices so the noise from the "sleeping" camera should be pretty easily detectable even when it's simply looking for motion.
Oh duh, yeah you are right. I had swapped RF and IR in my head for some reason when I was scanning the project page and thought this was somehow picking up signals based off noise from the sensor. Might be time for bed for me.
Game cams with cellular modems are getting to be pretty common, and you can equip them with solar panels. Basically just set em and forget em. It wouldn't surprise me if this is making them much more common...you can get them deep into the woods and don't have to go check on them hardly at all.
https://www.forestry-suppliers.com/c/trail-game-cameras/3-30...
Sigh, it used to be at least woods offered respite from ever-present cameras. I am starting to think I should stop trying to fight the impending 'Transmetropolitan' future.
Game cameras are truly pathetic.
Some applications are, sure.
The cameras themselves are useful for catching remote area | rural thieves on mine leases, rural properties, etc. They're great for spotting and counting rare and endangered species to better direct conservation efforts.
Quite a few people dumping their trash in the woods illegally have been caught in my area with them.
They just need to outlaw private citizens putting them on public property without a permit. Big fines could be a deterrant. Maybe USFS/BLM/NPS employees need some sniffing devices. The upshot is that if it's got a cellular modem, someone's paying a bill and they can usually be found pretty easily if you have the modem.
With fire seasons going the way they are west of the Rockies, I'd be a little concerned about a bunch of lion batteries scattered through the woods. Just takes one of them to blow up in late summer (say it gets crushed by a tree) and there's a good chance it'll be a multi-billion dollar problem that kills people.
Pretty much all the C and D rate state forests, nature preserves, etc, etc, in my state were only ever having their trails maintained by the "nominally illegal but nobody actually cares" SxS and ATV riders because the dog walkers and the hunters are much less averse to going off trail and even if they weren't they aren't packing a 15lb cordless chainsaw around to clear whatever fell on the trail.
Karens with game cams have done a lot to curtail this.
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This is dependent on the antenna. With a short 915 mhz antenna it picks up stuff 50 feet away. It auto calibrates on boot so if you’re in the woods I bet it would work really well. Just make sure you turn it on without a strong nearby signal.
Might also be useful for initial EMC compliance testing, maybe.
Does it get confused by nearby WiFi transmitters?
Cool project! I'd buy one of these if they were pre-assembled.
Thanks, it costs about 30$ in parts. Not sure what a fair price would be.
Rule of thumb in manufacturing is 5x BOM costs. This comment will be downvoted but only by people who have not been associated with a successful manufacturer.
I’d be happy to pay $150 for this.
That...doesn't sound unreasonable.
Not sure what the time/labor looks like, but I'd easily pay $60 bucks for that. You may be able to sell them at $100 and still move quite a few.
Honestly if you dressed it up a little you could probably charge quite a bit, it's just a matter of reaching that audience.
Agreed, I'd buy this at $100 for sure. I stay at a lot of airbnbs and am the kind of person who regularly checks those places for bedbugs.
i just disconnect the provided router in airbnbs i stay at. Turns out the host usually drops round all worried if there is a hidden camera.
It's sad we're letting bedbugs return.
Is the ESP32 mainly to drive the LCD display and provide a numeric readout, or is it also needed to control the sensor-side so that it cycles through different settings and frequencies?
It runs the screen and reads the sensors, you can see it in the code.
Interesting, thank you for sharing!
Maybe somebody knows: Is there something similar for the Flipper Zero?
I could make it I suppose.
This is ineffective against most recording devices.
"If you don't have a 9V battery, you can use a 9V battery."
lol, some bad summary there. It uses a lipo 3.7
it seems multiple ESP32s would fit into this giant case.
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