[ndsipa_pomu]

It doesn't strike me as that useful to have a hidden microphone in a KVM product as most of the time, they're going to be stuck in server rooms with just lots of fan noise to record.

Far more of an issue would be any kind of keylogger built into the software, which is why it's best to go for devices that support open source software.

[Y_Y]

just fan noise?

https://arxiv.org/abs/1606.05915

Any signal that you can modulate can be an exfiltration channel, and fan noise is no different.

[overfeed]

> Any signal that you can modulate can be an exfiltration channel, and fan noise is no different.

This KVM has HDMI input and can directly emulate USB mass storage; fan-modulation is the lowest-bandwidth (side-)channel available to the attackers.

[nine_k]

You can exfiltrate data from a machine which is not connected to the KVM. A high-security machine may be even air-gapped most of the time, but be physically nearby.

[close04]

I don’t think too many of these devices will end up in server rooms as opposed to home labs. And the ones that do end up in a datacenter are very unlikely to be allowed to ever reach the internet.

If the microphone was used for exfiltrating data, it would work against random targets that happened to let the KVM connect to the internet, and who have a nearby machine infected with some malware. That kind of non-targeted attack can be damaging but is semi-useless to the attacker.

[ndsipa_pomu]

I wonder if that's feasible in a room filled with many servers and fans going?

[runjake]

Yes, just modulate the fan noise on the transmitter, and apply a filter on the receiver.

[faidit]

Doesn't being able to modulate the fan presume you already control the target device?

[alextingle]

It's possible to get malware onto even air-gapped machines. This is a way to then communicate across the air-gap.

[PunchyHamster]

The KVM just uses a devboard that's also sold separately and just happens to have a microphone, given how cheap the mics are having one extra SKU would probably just cost them more than savings.

Also I wouldn't really consider it "server room" product. Pretty much any new server has KVM, this is more "a hobbyist needing KVM for their home server"

[ndsipa_pomu]

I can't recall seeing any server that includes KVM-over-IP, but instead they have some shitty remote access controller (e.g. Dell iDRAC) that is buggy as hell and requires a subscription to even get working.

[fsmv]

Supermicro boards have it via the IPMI Ethernet port. Doesn't require any sign up.

[ndsipa_pomu]

That sounds good - I thought they required a license key to get working.

(However, IMPI is a security nightmare with backdoors, default passwords and weak encryption)

[n5NOJwkc7kRC]

Intel AMT? Whatever AMD calls theirs?

[i_am_proteus]

It is possible to keylog via audio.

https://ieeexplore.ieee.org/abstract/document/10190721

[ErroneousBosh]

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.

[f1shy]

Do you have a pointer to learn more about the ATM keyboards? I would love to learn more about it

[CamperBob2]

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.

[NoMoreNicksLeft]

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.

[ndsipa_pomu]

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.

[ErroneousBosh]

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.

[n5NOJwkc7kRC]

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.)

[ErroneousBosh]

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.

[seszett]

It would take an especially perverse mind to keylog using audio on a KVM, though. The KVM basically has access to everything, any secondary spying using a microphone or a camera would provide very little added value.

[saltcured]

Maybe it's for the super secret stuff that the datacenter emergency ops worker knows not to type through the KVM? ;-)

[BenjiWiebe]

But the point of a device like this is that you (and your keyboard) are NOT physically present.

[hinkley]

They mean the K in KVM could trivially have a keylogger. For the computers attached to that KVM. Audio is for logging for computers not attached to the device in question. Which could be up to and including a whole server room save a couple machines.

[ndsipa_pomu]

What would you be able to get from the noise of loads of servers in a room where no-one is using a keyboard?

[Featherknight]

The conversations of server goblins ofc. Gotten listen in on the little gnomes inside the racks.

[hinkley]

I think I’m thinking of old school kvms you attach a laptop to instead of VNCing into.

[hinkley]

Ultrawideband never caught on because it turns out that the speed of light and sound in air is frequency dependent, so you have to know the distance to the target pretty accurately and then skew the signal to send or receive. (Imagine a phased array antenna but also with a frequency domain to work out as well).

But that doesn’t mean you can’t make it function in a loud server room. The whole point of it is working in and around noise.