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Comment by danbruc | Hacker News Reader

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

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> 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 ...

That's called playing the long game, and playing it quite cleverly!

Not really. It makes it clear from the first attempted sweep they altered construction -- the opposite of a long game.

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.

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.

> 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.

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.

> 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?

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.

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...

> 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.

Now you've got me wondering how common embedded RFID price tags are.

As I understand it clothes from Uniqlo have RFID tags in them.[0]

https://www.morerfid.com/uniqlo-rfid-tags/

it's not just electronics cause positives-- corroded metal does too, anything that forms a semiconductor can get detected.

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.

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...

Here [1] are some pictures and additional details on NLJDs. You can get your own, for example the Orion 2.4 [2] for USD 15.2k (free shipping) [3].

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

[2] https://reiusa.net/nljd/

[3] https://spyassociates.com/orion-2-4-non-linear-junction-dete...

Oh good, I really wasn't prepared to pay the $7 for shipping that.

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?

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