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A comment on How I discovered a hidden microphone on a Chinese NanoKVM. Parent comment

Re:How I discovered a hidden microphone on a Chinese NanoKVM by ErroneousBosh on Saturday December 06, 2025 @11:08AM (#46174381)
A long time ago (maybe in the mid-90s) I knew an elderly radio amateur who could not just "copy" CW by ear, but also RTTY. He could also pretty much tell what a teleprinter was printing just by listening to the noises it made, like he'd be facing away from it on the other side of the room reading out entire words from what was coming through.

Apparently in the 50s when he did his National Service he'd been in the Signals but "not in the regiment that's on his papers", make of that what you will.

I have noticed that with PSK modes and particularly PSK31 you can hear "CQ CQ CQ" as a distinctive pattern much in the same way as it is with CW.

IBM spent a fortune developing ATM keypads that - when correctly mounted - had keys that made the exact same noise no matter how you pressed them or how worn they were.

So I don't doubt that someone suitably clever could extract audio from a room and work out what was being typed.

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Re:How I discovered a hidden microphone on a Chinese NanoKVM by f1shy on Saturday December 06, 2025 @11:15AM (#46174443)
Do you have a pointer to learn more about the ATM keyboards? I would love to learn more about it
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Re:How I discovered a hidden microphone on a Chinese NanoKVM by ErroneousBosh on Saturday December 06, 2025 @11:57AM (#46174759)
Maybe. They were necessarily very cagey about it back then, but I might have some documentation kicking about in storage. I tended to keep copies of every service manual I could get my hands on back then.
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Re:How I discovered a hidden microphone on a Chinese NanoKVM by CamperBob2 on Saturday December 06, 2025 @04:10PM (#46176620)
One really-cool way to solve that problem is to embed a 7-segment LED under each keycap. You walk up to the keypad and the 0-9 digits appear in random order. No one can shoulder-surf, look for wear or IR emission from the buttons, or train on the click sounds.

Dell had those on every lab door in the building back in the early 90s. You felt like 007 every time you punched in your access code. I've never seen them anywhere since.

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Re:How I discovered a hidden microphone on a Chinese NanoKVM by NoMoreNicksLeft on Saturday December 06, 2025 @04:31PM (#46176762)
And now days I can't put in my card's pin without 10 overhead cameras aimed at the register area. All the cameras of which are network-connected, video stored persistently, and high res/fidelity enough to here the little beeps as I press the keys, and to know that I've hit the enter because the screen indicates it immediately. But then Dell cared about its own security, and the grocery store doesn't give a single shit about whether my life is ruined by identity theft.
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Re:How I discovered a hidden microphone on a Chinese NanoKVM by ndsipa_pomu on Sunday December 07, 2025 @07:26AM (#46181242)
That's why I always cover the pin pad with my other hand (probably also holding my wallet) when putting in a pin. However, I think the more likely scenario to defend against is shoulder surfers - the pin by itself is useless until combined with the card, so physical presence is needed to lift the card from me.
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Re:How I discovered a hidden microphone on a Chinese NanoKVM by ErroneousBosh on Sunday December 07, 2025 @05:08PM (#46185713)
Contactless doesn't need a PIN, and indeed if it's looking for one that's a good indication that the card reader is compromised and skimming.
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Re:How I discovered a hidden microphone on a Chinese NanoKVM by n5NOJwkc7kRC on Monday December 08, 2025 @03:32PM (#46197254)
The Austin airport has, or used to have, such keypads in places. (Doors from the baggage carousel area through to the airside ground staff areas, for example.)
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