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Comment by varispeed | Hacker News Reader

Wouldn't that tell any spy device / software that the subject has switched off the means he or she can be surveiled by? I cannot see how this could help with anything. They should rather do a physical switch that would 0 the data lines from these devices, so that camera or the microphone would be seen as working, but not sending any signal. Even better if you could pre-program some kind of ambience sound and pre-recorded cam video, so that once you turn it off, the perpetrator will think that they are still getting something.

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Why would you care about fooling surveillance? The goal is to prevent a potential adversary from getting any video/audio footage, them being aware of you actively blocking any attempts is not really relevant.

Besides, the vast majority of users will not be under active attack. Having an on-screen popup when you try to use the webcam telling you that it has been hardware-disabled is quite a must-have. If you don't have something like this, you'll get a lot of support calls which boil down to "you accidentally pressed the kill switch, press it again to re-enable".

> Why would you care about fooling surveillance?

For example, when you are "required" [1] to run surveillance software on your computer.

[1] https://www.vice.com/en/article/n7wxvd/students-are-rebellin...

...then you just cover the camera and/or mic with a physical cover, such a piece of tape.

> and/or mic

How well would tape work on that?

These exam proctoring softwares are only required to be run during the time you are actively taking an exam. The rest of the time, there would be zero issue for a student with hardware disabled camera and microphone.

The invasive proprietary software used to prevent cheating cannot be trusted to work only when the students want it work. Its purpose can and will be twisted to fit the agendas of whoever owns the software. It probably introduces several security vulnerabilities into the system just by being installed.

It's a Chrome extension.

> If you don't have something like this, you'll get a lot of support calls which boil down to "you accidentally pressed the kill switch, press it again to re-enable".

Yep. This was an extremely common issue in the mid-2000s, when laptops started integrating wireless hardware with hard power switches, often on the side of the laptop where they could easily be toggled by accident.

But was it a "fault" of the switch itself or lack of meaningful feedback that the switch was engaged? It seems like they have not implemented it properly and then say it wasn't a good idea, without really giving it a chance.

It might be for usability reasons: having your video conferencing application tell you "Your webcam appears to be disabled by the privacy switch, is that intentional?" probably saves a lot of time in tech support calls.

Also, having your video conferencing application send some prerecorded audio and video data to your colleagues because you inadvertently turned the kill switch would not be a highly desirable outcome.

Unless you record infinite video and sound it's pretty easy to check if the video is a loop. Even static video of an empty room would have variations over time while a recording would be identical. Even auto-generated audio and noise would have a pattern which can be matched on. And if an attacker has control over your machine they can trivially correlate it with other activity to detect fake input.

It's basically a false sense of security which is generally worse than doing nothing.

If you can pattern match all auto generated audio you can prove there’s no one way functions and that cryptographic hash functions don’t exist.

Detecting the pattern in a prng stream is equivalent to finding its Kolmogorov complexity. https://en.m.wikipedia.org/wiki/Kolmogorov_complexity#Chaiti...

You're not pattern matching all auto-generated audio. You are pattern matching the audio generated by a specific algorithm. An attacker who has access to your microphone will know which laptop you have and what hardware it has.

This assumes an attacker is targeting you specifically since otherwise this is all moot (a broad attack could care less as to why your microphone is off).

You wouldn't be using a PRNG for this, because what would be the point? The idea would be to generate some plausible-sounding audio, not garbage that a listener would obviously know isn't real.

Really, though, in general there's just no point to this altogether; just cutting power/data to the mic is fine. There's no need to attempt to fool someone with fake audio, outside of some very edge-case scenarios that I'm sure Dell (rightly) does not care about.

>Wouldn't that tell any spy device / software that the subject has switched off the means he or she can be surveiled by?

And the spy device/software knowing the user has "switched off the means" vs "they are broken" is important because?

>They should rather do a physical switch that would 0 the data lines from these devices,

What exactly do you expect that to accomplish. Anyone actively targeting you getting literally NO SOUND OR VIDEO is going to know that you've flipped the switch just the same.

Even the quietest apartment has HVAC that will be picked up. If they're recording for hours they're going to hear people walking by. The camera itself will still provide an image, even if it's black, that looks different than no signal at all.

That's why the idea of having some pre-recorded stuff on tap, but sending no signal could waste some of the perpetrators resources, which I think is something nicer to have than letting them know it is switched off.

Sorry but if you're going to those lengths you should be buying a laptop without a camera or mic. Do video calls from your phone and put it in a soundproof/wireless transmission proof box.

If a nation state is able to get to your laptop they're going to figure out pretty quickly that you're "feeding something pre-recorded" into the mic and camera every time you have a meeting. Ignoring the insane effort you'd have to put out to feed that in and make it even semi-believable. For starters they are presumably tracking who you're meeting with - are you going to have a meeting before your meeting to pre-record? Hope they don't figure out that you're saying the exact same thing in two different meetings? Somehow have root on your laptop but aren't bright enough to figure out you're feeding data from a local file into your mic and camera?

Thank you! Great answer

I believe the switches are there for the user as a simple way of activating or deactivating the microphone and camera and for them to know (via LEDs) the current state.

If you have a spy device connected to your computer or have malware running, you are very screwed in a million different ways already. Limiting knowledge of hardware state to malware doesn't buy you much.

If it is switched off, then you cannot be surveiled by it. Mission accomplished.

I belive you can blacklist that driver if needed.

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