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How I discovered a hidden microphone on a Chinese NanoKVM

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Re: How I discovered a hidden microphone on a Chinese NanoKVM

#101

Post by simoncion »

jlward4th wrote: post #84
stragies wrote: post #17

Earlier quoted context omitted.

Why did you not just login to the device, and switched off "Broadcast to multicast", or changed the destination address? Edit: Some brands of Network-KVM use this, so that you can control the target device from another device, like e.g. an App on a tablet. That way you don't have to stand next to the target device in the noisy and cold machine room

The KVM didn't have any documentation on anything related to its network interface. I ran a port scan on it but didn't know if there was a way to log into it.

> The KVM didn't have any documentation on anything related to its network interface.

My research disagrees. See [0]

[0] https://news.ycombinator.com/item?id=46177462>

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#102

Post by nixpulvis »

milesvp wrote: post #88

Mics have a pretty standard look, and are hard to miss on the board. It would be more insideous if there were cheap film caps leading into a very expensive ADC. I work with with analogue audio, and it’s very important to design around the noise of cheap caps. They are for all intents and purposes microphones and if you were clever about different caps for different frequencies and good digital processing I have no do…

Why is there a component on the board that isn't used in the product for any official purpose then? Even if you believe it was an accident and an oversight (which it could have been), you should be upset because it's something that could be pretty serious if you used in your home.

Just because you might claim it's not malicious, doesn't make it not negligence.

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#103

Post by stragies »

simoncion wrote: post #100
stragies wrote: post #97

Earlier quoted context omitted.

Was the network port bridged to both PCs all the time (as the description makes it sound, or did only the "active" PC get a functioning network connection? Could you tell from the FDB of the upstream device, if there were more than two MAC addresses active on the port? Did you (hopefully) open it up and make PCB pictures before chucking it?

This picture from the list of product pictures [0] indicates that the thing acts as an Ethernet bridge. It probably exposes itself as a USB-C gigabit Ethernet device to the machine it's plugged into. Page four of TFM [1] supports this theory. Also, this functionality is called out in the product listing and in the manual. I'm over here laughing my ass off because OP got so frightened by this clearly-documented featur…

The manual, as OP said, does not offer any explanation, why the device might show up with an additional MAC/IP at the upstream switch port, and which services it might offer. OP sounds knowledgeable enough to be able to exclude the possibility, that the additional MAC/IP could be from one of the PCs, like e.g. when playing with VMs using an internal bridge in the Hypervisor.

Maybe the device has a bigger "cousin" device, that includes "control via APP", and this feature was not properly/fully disabled on this one.

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#104

Post by faidit »

runjake wrote: post #44
ndsipa_pomu wrote: post #35

Earlier quoted context omitted.

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

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

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

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#105

Post by heavyset_go »

mintplant wrote: post #67
Rygian wrote: post #66

Earlier quoted context omitted.

"hidden microphone in a Chinese KVM" is the correct way to describe what is going on. "Reusing existing stock" is not a valid excuse. They are currently selling this device without advertising that it contains a working microphone.

A working microphone and recording software and hacking tools like aircrack-ng on an otherwise stripped-down OS image...

Vendor BSPs are horrible, it would not surprise me if tools like that were included with it.

I used one that included everything in C:\Users\\Desktop in it.

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#106

Post by margalabargala »

knallfrosch wrote: post #98
Milpotel wrote: post #5

> [...] and runs a heavily stripped-down version of Linux that lacks systemd and apt. And these are just a few of the issues. ?!

Lacking software (apt) is a security issue. Having software installed (tcpdump) is also a security issue.

Could you elaborate on how lacking apt is a security issue?

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#107

Post by firesteelrain »

heavyset_go wrote: post #105
mintplant wrote: post #67

Earlier quoted context omitted.

A working microphone and recording software and hacking tools like aircrack-ng on an otherwise stripped-down OS image...

Vendor BSPs are horrible, it would not surprise me if tools like that were included with it. I used one that included everything in C:\Users\ \Desktop in it.

Was it made in China?

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#108

Post by milesvp »

nixpulvis wrote: post #102
milesvp wrote: post #88

Mics have a pretty standard look, and are hard to miss on the board. It would be more insideous if there were cheap film caps leading into a very expensive ADC. I work with with analogue audio, and it’s very important to design around the noise of cheap caps. They are for all intents and purposes microphones and if you were clever about different caps for different frequencies and good digital processing I have no do…

Why is there a component on the board that isn't used in the product for any official purpose then? Even if you believe it was an accident and an oversight (which it could have been), you should be upset because it's something that could be pretty serious if you used in your home. Just because you might claim it's not malicious, doesn't make it not negligence.

So usually you would DNP the parts and they wouldn’t populate at the factory. But sometimes you have a bunch of boards already made that for some reason you can’t use for another SKU, and so you put them in another housing, and change the board for the next rev.

Mind you, I’m not saying a mic in a KVM isn’t sus, just that it’s a little obvious, and certainly not stuxnet level espionage.

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#109

Post by FateOfNations »

knallfrosch wrote: post #98
Milpotel wrote: post #5

> [...] and runs a heavily stripped-down version of Linux that lacks systemd and apt. And these are just a few of the issues. ?!

Lacking software (apt) is a security issue. Having software installed (tcpdump) is also a security issue.

apt is a package manager. It's only relevant if the system uses it to manage it's packages. Red Hat based distributions, for example, don't use apt. Embedded devices typically don't manage packages on an individual basis, rather updating the entire distribution via "firmware updates".

Re: How I discovered a hidden microphone on a Chinese NanoKVM

#110

Post by tosti »

15155 wrote: post #74
Y_Y wrote: post #23

Earlier quoted context omitted.

I don't know what you mean here, I can plug a speaker into my mic slot and use that to record, just as plugging a mic into the speaker slot gives a (crappy) speaker.

A DAC and amplifier circuit is electrically incapable of processing input (on its own.) Physically unplugging and moving a speaker to a mic input works, sure, but very few devices can do this switching electronically.

I think most intel HDA compatible chips can do this. You can specify which pins are connected to what.
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