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Show HN: RF Hunter – Find hidden cameras and other devices (github.com)

594 points by RamboRogers ↗ HN
This 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.

186 comments

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Terr_
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?
RamboRogers
It runs the screen and reads the sensors, you can see it in the code.
transpute
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.

bobmcnamara
Generally, directionality is tricky to do handheld over a wide bandwidth.

Another approach is a phased rx array, could even be as few as 2 antennas, and from that you get a bearing too.

amatecha
May I introduce you to: the Log-periodic dipole array antenna[0], allowing quite a broad response range with decent directionality in a single antenna. There's probably a practical limit to just how broadband you can make one, but just from a quick search I found one commercially-available antenna[1] that covers 120mhz-2.5ghz, for example.

[0] https://en.wikipedia.org/wiki/Log-periodic_antenna

[1] https://ara-inc.com/product/lpd-tactical/

bobmcnamara
Didn't read it, but it's going to be poor directivity for that meager bandwidth.

If you're going to go with that wide of a beam why not use a single element and wave it around?

I should also mention the third trade off, size, plays into this tool.

kubectl_h
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.
etrautmann
Don’t many of those just store data locally?
kubectl_h
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.
ffujdefvjg
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...

A4ET8a8uTh0
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.
jamil7
Game cameras are truly pathetic.
defrost
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.

ffujdefvjg
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.

potato3732842
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.

toss1
Agree, if you are talking about hunters (and I feel the same about fish-finders). To them: dude, if you're going to hunt or fish, don't just cheat, learn the craft.

For my purposes, I've found a game camera extremely useful for finding what and when various critters are eating the garden and other plants in the yard, and to figure out what discouraging and diverting measures actually work. I also get a few pretty cool wildlife pics I'd never otherwise get.

themaninthedark
So just curious; if a hunter has a limit of 1 buck and 2 doe but he really only needs 350lbs of meat, so either 1 large buck and smaller doe or all 3 if they are smaller. Should he give up using the trail camera and the knowledge of if there is a large buck out there and just kill the first 3 deer he comes across?

Another question, do you look up salary stats on Glassdoor, etc before you consider open position or asking for a raise? Would you consider it offensive if someone told you to stop cheating and just learn to negotiate better?

kubectl_h
Not to be pendantic, but if we are talking white-tailed deer, it depends on the population characteristics of the area you are hunting. In many places in the US the game management departments would probably prefer multiple doe if you have more than 1 tag.

Additionally if you are hunting for sustenance, as in you really need the meat, then you take the first deer you can find. Waiting for the ideal deer is a good way to not end with a deer at all, regardless of whether you have them on camera or not.

toss1
Or maybe, instead of relying on yet another toy of modern technology, do it the same way it was done before game cameras?

Learn the craft so that you can tell from the signs, such as tracks, droppings, markings, etc., and spend the time doing actual scouting and sightings before hunting?

Seems to me you're either enjoying the whole process of learning and doing the sport, or just enjoying the results. If the former, do it for real, if the latter, just buy some game meat from someone who does. Doing everything with excess technology and little craft seems more like cosplaying and just cheating yourself of a real experience.

toss1
and on your other question

>>do you look up salary stats on Glassdoor, etc before you consider open position or asking for a raise? Would you consider it offensive if someone told you to stop cheating and just learn to negotiate better?

I'd look at Glassdoor as reading the actual signs in the wild, like reading tracks, markings, broken twigs, etc., not an artificial aid — it's one of the signs in the environment. And like signs in the environment, it's not like a camera, it is often obscured, gamed, and skewed. Similarly, a crafty employee would also contact people she knows and exploit connections to scout the potential employer.

However, putting game cameras, webcams, and/or recording devices in their management offices, HR offices, and meeting rooms would be considered a bit out of bounds, you think?

potato3732842
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.
05
Not really, those are using PIR motion sensors to wake up, so you'd need to be able to capture the burst of activity when the camera actually wakes up and takes a picture. PIR circuit is very low power, so not much RF energy to detect while it's sleeping..
potato3732842
The unshielded electronics are still going to be highly RF reflective the same way that a car headlight is still reflective when not powered. Pretty much all bug sweeping works on this premise.

Finding a game cam in the woods with basic bug sweeping equipment is like finding a headlight housing on the ground in the woods at night using a flashlight.

05
> highly RF reflective

What do you mean, exactly? Most of what you can find in the forest is 'RF reflective' because of the water contents - the trees, the grass, the ground. What's the proposed detection method that is going to discern a reflection from a small PCB from a reflection from a large tree trunk?

edit: first, the camera isn't a retroreflector so you can't just light it up from any direction and get a strong reflection. Second, the kind of equipment that would give you good directionality with a static target is some next generation beam steering radar, that stuff is so expensive you're better off walking around with a 4K camera and then processing the footage with an image detector to find possible matches with images of trail cameras.

RamboRogers
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.
o1o1o1
Interesting, thank you for sharing!

Maybe somebody knows: Is there something similar for the Flipper Zero?

RamboRogers
I could make it I suppose.
x______________
I've been lurking yc for a while and you inspired me to reach out to the community..

This would be pretty awesome, please advise if there's anything I (or anyone) could do to support you in getting this logic onto a flipper (project support, testing, etc).

-x

RamboRogers
Okay, I don't think it would be hard, most of the Flipper Modules use some sort of ESP module like an ESP8266 for the Wifi module.

I've got a flipper right here. I find it cumbersome to use, but it's a pretty popular consumer product. I'll look at what the wiring cost could be to print a board. I've never done that.

o1o1o1
First of all, I also would be very grateful if you can make this happen. I don't have too much free time currently and also no skill in hardware, but if there is anything else I can help with, I'd be happy!

Why do you find it cumbersome to use?

ffujdefvjg
Cool project! I'd buy one of these if they were pre-assembled.
RamboRogers
Thanks, it costs about 30$ in parts. Not sure what a fair price would be.
ffujdefvjg
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.

_dark_matter_
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.
woleium
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.
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bbarnett
It's sad we're letting bedbugs return.
tomcam
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.

Eisenstein
But does that work for putting together what are essentially modular pre-assembled boards? The RF detector, display, charge controller, and ESP are already consumer parts, and they are put together not unlike how a desktop computer can be built from retail parts. Would you say that 5x retail cost for the parts is fair for a custom built PC?
tomcam
The custom PC components are already finished goods by the time they get to your PC assembly person. Most of the markup is already baked in. I would in fact expect to pay $120 or so to have a PC assembled for me, so we still get to the $150 figure in either scenario. I assume you have never worked for, or originated, any such business. That $150 has to cover overhead like assembly labor, rent, credit card charges, insurance, accounting, bookkeeping, excise tax, chargebacks and refunds, advertising, website development and social media, bookkeeping, software subscriptions, fulfillment, compliance, and so on. Running any business in the western world is complicated and expensive these days.

If you’re imagining you can take $30 worth of parts, sell the finished item for $60 or $90, and sustain that enterprise, it’s time to reconsider your business acumen.

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ted_dunning
There's a lot of ways to rephrase this to be less insulting.

For instance,

"lots of people have started with the idea that they could sell at retail for only 3-4x parts cost and failed"

or

"I have had personal experience trying (and failing) to drive down retail cost of electronics below this rule of thumb"

This last has the advantage of making the advice more personal.

tomcam
> "I have had personal experience trying (and failing) to drive down retail cost of electronics below this rule of thumb"

Didn't have to make such a statement because I paid attention to people who knew what they were doing. If someone had been this "insulting" with my attempt to beat Craigslist, OTOH, I'd have saved $1.4 million of my own money. I'm happy to be "insulted" by people with more experience.

Eisenstein
Or you can just admit that you don't care about other people's feelings.
tomcam
You have an active imagination. I like that in a budding social critic of your skill level!
Eisenstein
Since you are asserting that you do care about how you impact others, I would like to point that you have acted contrary to that assertion in our conversation. In particular, your:

* use of dismissive sarcasm ("active imagination") to deflect legitimate concerns

* deliberate infantilizing tone ("budding social critic of your skill level")

* preemptive dismissal of differing viewpoints ("This comment will be downvoted but only by people who...")

* assumption of others' inexperience ("I assume you have never worked for...")

* defensive response claiming that you have the right to be insulting to others ("I'm happy to be "insulted" by people with more experience.")

If you honestly do care about how you come across in your communications and have a desire to use your interactions with others productively and not in a way which comes across as bullying, I am happy to work with you privately towards this goal. Is this something you would be interested in?

tomcam
Thanks kindly, but my dance card is full.
declan_roberts
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.

RamboRogers
Well, maybe - it would need to have ir enabled. This also detects listening devices etc.
mbreese
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.

ddingus
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.

Ballas
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...

deknos
do you have examples of cameras or smartphone which do not have IR filters?
Ballas
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...

ddingus
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.

botanical76
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.

lightedman
Easy test - check your black levels against someone wearing a black fabric or a reflective black surface. If you get a fair bit of grey in the image, odds are very great that you don't have an IR filter installed.
runjake
Lies. :-)

Somewhere in my HN comment history from a while back is a response to a person claiming that modern phone cameras can’t detect IR illumination and remotes.

I took a bunch of modern iPhones and Android phones, from colleagues in an IT dept, and demonstrated they can in fact see a bunch of different IR remotes and illuminators with the rear camera.

I could find zero cameras that could not see the IR.

I’m not sure where people got the notion they couldn’t.

JKCalhoun
Guessing because they read that CCD's have IR filters on them.
pwg
The ultimate answer is "it depends". And upon what it depends is the particular IR wavelength the camera emits to "illuminate" a scene in IR for night photography.

My cell phone's back camera will show IR light from IR remote controls (I've used it for just that to verify that a remote is transmitting). But I also have an outdoor IP camera with IR illumination in my back yard. The same cell phone camera sees zero IR emitted from the outdoor IP camera (even though it quite well lights up a fairly broad area of the yard at night).

So for my phone, if a 'spy cam' were using the IR wavelength the IP camera uses, I would never know it was present by using the phone camera. If it used something closer to the wavelength used by IR remotes, yes, then the 'spy cam' would light up via the phone camera.

lightedman
"I’m not sure where people got the notion they couldn’t."

I make IR devices. My phone is the only one in the warehouse that can pick up their emissions - everyone else's cameras have IR filters with what appears to be a sharp ~750nm cutoff. I'm the only one that will pick up 800-1064nm with my cheap Samsung, and so I'm the only one doing the testing on those diode assemblies.

Ballas
Ok, I'll admit that I have not tested that many phones, but all the phones I had in the last ~8 years would not detect my remotes unless I used the front camera. That could very well be because all the remotes I tested operate on 940nm instead of 850nm (the two common options), and the IR filter in my devices are so that it would cut the one but not the other. Or that they just have a much lower power level. Either way, most modern phones that double as cameras will have an IR cut filter of some sort, otherwise some photos appear weird - like the red glow from a fire will appear purplish-white.
alwayslikethis
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.
declan_roberts
That's exactly right, and part of that is because they're cheap and put off some visible light.

Thankfully the perverts who put this stuff in airbnbs just go to amazon and search and buy cheap stuff, which is easy to detect.

kube-system
The lower wavelengths like 850nm IR LEDs are visible. Some cameras use higher wavelengths like 940nm IR LEDs and they aren't.
jmward01
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.
rahimnathwani
> 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.

Cthulhu_
A burglar isn't deterred by a camera though. I mean for this use case they'd already be inside. Cameras don't prevent nor solve crime, at best they're for legal purposes if someone is caught, or for insurance claims.
kube-system
That sentiment has selection bias built in. Anyone who commits any crime wasn't deterred by everything.

It is, however, factual that people choose to behave differently when they know they are being recorded. That might mean choosing not to commit a crime, commit it elsewhere, destroying a camera, or wearing a mask. While a functional camera can't prevent crime, it can identify those who commit them.

RamboRogers
This Device lights up pretty good on wireless or cellular data transfer. If my wife starts browsing on her phone it lights up.
ddingus
Of course nefarious actors will ignore the requirement and or hack their gear.
bbarnett
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.)

rkagerer
"If you don't have a 9V battery, you can use a 9V battery."
RamboRogers
lol, some bad summary there. It uses a lipo 3.7
ujikoluk
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!

transpute
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.

ujikoluk
Oh neat! Yes that's the kind of imagine I want to see
coin
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.
KeplerBoy
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.

killingtime74
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
KeplerBoy
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).
RamboRogers
It doesn’t say “all”, it also doesn’t detect a someone in the closet, unless they’re transmitting.
yftsui
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?

transpute
> TinySA

What's the frequency range and scanning speed of TinySA?

garblegarble
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

Cthulhu_
That camera detector is pretty pricey; I once saw a low-tech solution that was basically a dyed card that you had to put in front of your phone camera with the light on, the light reflected by the camera lens would become very visible.

Of course, only a matter of time - if they don't already exist - before there's cheap spy cameras without a reflecting lens, like a solid state camera of sorts. I believe some years ago they were experimenting with that as an alternative to a front facing camera on phones.

rapjr9
Look for "bug detector" on eBay, there are lots of RF and optical camera detectors and they are fairly cheap. They work, at least so far as detecting steady streams of WiFi data, and cellphone transmissions, I've tried a couple of them:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p4432023.m...

The optical camera detectors work based on a simple idea, red LED's are used to create a circular pattern of light and you look through a red filter at your space. A camera lens is concave and symmetric so it reflects the LED's in the same circular pattern. Blink the LED's. Look through the red filter and scan around the room. Anything that reflects a discernable circular blinking LED pattern is a lens or lens like. Basically it makes it easy to see everything that reflects light symmetrically back at you. Move around a little and anything with a lens will stand out. It only works with fairly large lenses though, a pinhole camera would not be detectable.

Their RF detectors have adjustable sensitivity and indicate amplitude of the signal. Good enough to track the transmissions back to the source, though they don't provide any frequency information. Range is somewhat limited so you have to move around a room to scan it.

TinySA works well for detecting RF sources also. I don't know what the exact update rate is but the one I have seems to update at least a few times per second. It's a little tedious to use, the RF spectrum is big and you'll find quite a few spikes from sources in it and you have to zoom in on each one to get the exact frequency and observe how it behaves (or maybe there is a way to select a peak of interest? I haven't played with it much.) You'll find FM radio stations, cellular communications, cordless phones, and lots more.

Most people are not going to be finding surveillance bugs in their homes or offices. However these things are useful for understanding what your RF environment is like or troubleshooting RF devices. Might be good for telling if your smart appliance is spying on you, for example if the detector beeps every time you change channels on your TV.

mschuster91
> Most people are not going to be finding surveillance bugs in their homes or offices.

Sadly, hidden cameras, microphones or other forms of espionage in the workplace are rare but not unheard-of in the recent past, e.g. Wal Mart [1] or Lidl in Germany [2]. Any shop with a tradition of union-busting I'd assume to be filled with all possible sorts of surveillance by default. On top of that come the sex pest cases like [3] - and these have exploded in the last years now that tiny bugs can be had for tiny amounts of money on Alibaba and whatnot.

[1] https://en.wikipedia.org/wiki/Labor_spying_in_the_United_Sta...

[2] https://www.spiegel.de/wirtschaft/stasi-methoden-beim-discou...

[3] https://www.nn.de/erlangen/erlanger-chef-filmt-kolleginnen-m...

slow_typist
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

RamboRogers
It doesn't detect short burst well at all. It does detect traffic over a second or so, like a TCP session of an h264 stream.

https://www.amazon.com/dp/B07FHZXTCZ?ref=ppx_yo2ov_dt_b_fed_...

Specifications: Working frequency: 1M--10000MHz Measurement power: -55dBm to -0dbm Output voltage: 0.33- -1.65V Detection slope: -22mv/dBm (typical value) Input impedance: 50Ω Supply voltage: 7-15V Size: as the picture Weight:7g

9dev
While researching for parts, I also found this one: https://www.amazon.com/dp/B07RR86PFC/ It goes up to 10GHz, and it operates on 5V. Would that also be an option, and possibly allow to get rid of the boost converter too?
slow_typist
Thanks OP. The detector itself has a Pulse response time of 6 ns/10 ns (fall/rise) but of course the whole system will always be slower. 1 s is a lot though, got probably nothing to do with the sampling done by the esp.
transpute
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:

  USB hubs
  AC power strips
  SSD enclosures
  monitors
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goodpoint
This is ineffective against most recording devices.
RamboRogers
Only if it’s transmitting, this detects rf. It can’t detect ears.
goodpoint
...and only if the transmission is frequent enough.
RamboRogers
100%, it needs to transmit pretty much constantly. Something like an H264 stream or an audio stream via TCP or UDP over something like wifi.
amelius
Does it get confused by nearby WiFi transmitters?
RamboRogers
It baselines on power on. So you'll need to get closer to raise the baseline. It also doesn't seem to alert on beaconing (or very little), my wifes phone and other devices need an active transfer to trigger it. (more than a 1/2 second)
amelius
Might also be useful for initial EMC compliance testing, maybe.
beardyw
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.
severino
> They have differing start up sequences which using the wrong one leaves a blank screen.

You mean, bricked?

beardyw
No, just no clue why it is unhappy.
danbruc
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

amelius
> 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 ...

mxuribe
That's called playing the long game, and playing it quite cleverly!
daveguy
Not really. It makes it clear from the first attempted sweep they altered construction -- the opposite of a long game.
krisoft
That depends on what the game is. For example if they wanted the embassy to stay in their old already compromised premises they achieved that. (for about twenty years at least.) If they wanted the USA to spend a lot of money they also achieved that.
emmelaich
They knew about the devices in 1985, a few years after construction started in 1979 and construction didn't finish till 2000. They probably knew earlier than 1985. So it probably wasn't a big deal and would've cost the SU a lot and they were less able to afford it.
krisoft
> They knew about the devices in 1985, a few years after construction started in 1979 and construction didn't finish till 2000.

That happened due to the bugs found. This is the point I'm making. If your goal was to keep them where they were already are (Mokhovaya House) then the bag full of diodes mixed into the concrete did that perfectly for like 15ish years.

> They probably knew earlier than 1985.

Doesn't change that argument.

> So it probably wasn't a big deal and would've cost the SU a lot and they were less able to afford it.

We are talking about a few bags of diodes vs rebuilding three stories of the building with imported workers. This was a very cost efficient attack.

hoistbypetard
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.

diggan
> useful in most environments today because our homes and offices have false positives littered all over the place

Like the structural elements in your house/apartments have something similar to diodes in them, or what are you referring to?

hoistbypetard
I think a lived-in place has enough stuff in and near the walls to make this kind of scan less than useful. We have things hanging on the walls that'd distort it. Maybe an empty one would be OK now, but I think the ecobees all over the place would even distort it for those.
mannykannot
I had a vague recollection that rectifiers for battery chargers were once made out of stacked layers of oxidized copper disks, and then, in the article danbruc linked to, I saw this:

Note that other semi-conducting materials, such as a rusty nail or an oxidised piece of metal, also generate harmonic frequencies and may there­fore cause an NLJD to generate a false positive.

https://www.cryptomuseum.com/df/tscm.htm#nljd

It turns out that the rectifiers in question were copper - cuprous oxide - lead sandwiches:

https://hackaday.com/2022/04/20/copper-rectifying-ac-a-centu...

gorjusborg
> our homes and offices have false positives littered all over the place

Sure, but location matters. Searching weird (for electronics to be), but line-of-sight places (like a bookcase) you might still have a good signal to noise ratio.

nullc
it's not just electronics cause positives-- corroded metal does too, anything that forms a semiconductor can get detected.
alwa
I wonder if it would be feasible, with modern techniques and sufficient motivation, to map where the “background” diodes ended up setting in the concrete; then to measure newer sweeps against that baseline.
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inglor_cz
Several days ago, a long interview with the former Czech ambassador to Moscow, Vítězslav Pivoňka, appeared in Czech newspapers. Unfortunately it is mostly paywalled. [0]

As you could expect, bugs everywhere, but some were used for intimidation. E.g. he says, on a weekend morning, we were still in bed with my wife, when a cuckoo started cuckooing out of a wall. Yeah, it was a bug, and it was meant to emit sound and make you more nervous: "we know about everything that happens in your bed".

He said that the Russians never cross the red line of actually physically manhandling diplomats, but as far as bugs and psychological pressure go, there is nothing off-limits.

[0] https://denikn.cz/1549047/deptali-ho-kukanim-a-ponizovali-ha...

AlanYx
Are nonlinear junction detectors still state-of-the-art for detecting hidden devices when powered off? Does anyone know if alternatives like electronic noses (to detect chemical signatures associated with IC packaging) and magnetic anomaly detection increasingly used for this?
[dead] 7bit
[flagged]
thih9
Does anyone have a personal experience with finding a hidden camera in an AirBnB?
lynx23
Well, not in an AirBnB, but... Already years ago, they found one in the ladies room at work...
RamboRogers
I found someone with a pen recording me. They left it on the desk, and I took it by mistake. I found it in my kit and realized it was a spy device.... yikes.
binarymax
Yes, but it was obvious and I didn’t use equipment. It was in Jan 2020 at an Airbnb “hotel” in Nashville. There were two smoke detectors in the room. One of them was not like the other. I wrapped it in toilet paper. I left it wrapped so the owners knew that I knew, but I didn’t bother reporting it because I rarely used Airbnb and it was a last minute trip. And then the pandemic hit and that was that.
JKCalhoun
> There were two smoke detectors in the room. One of them was not like the other.

I imagine too that the other was not like the one. ;-)

marsh_mellow
Very cool! Could this work for detecting nearby drones?
RamboRogers
I would think it would work really well for that usage case. You could tune the antenna to focus on the in use bands. The automatic baselining solves a lot of this.