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Comment by hyko | Hacker News Reader

Here’s the document explaining how it’s physically impossible to use the microphone when the MacBook lid is closed: https://support.apple.com/en-gb/guide/security/secbbd20b00b/...

Where is the equivalent document explaining how it’s physically impossible for the camera to be active without the green LED lighting up?

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They also claim that if you add a (MFI-compliant) case to the iPad, and close it, that this similarly disconnects the microphone. The simplest mechanism to do this sounds complicated enough that it reduces my confidence in the mechanism. The point of half the comments in this thread is that a hardware interlock mechanism needs to be dead simple. This sounds like a step in the wrong direction.

How could a complicated mechanism compared to no mechanism be a step in the wrong direction?

The whole point of this thread is that Apple is telling us to not rely on dead simple devices (camera covers, tape, etc.), and instead to trust their internal mechanism that they claim can't be beat. If people take them at face value, but the mechanism is in fact complex enough to admit an exploitable vulnerability, that's a net loss of security, and is a step in the wrong direction.

But you are talking about microphones which you cannot simply cover.

I admit, muffling them is better than nothing – but in the case of microphones Apple doesn’t even advise you not to cover them.

Either way, this is just an effect of common covers seemingly breaking screens. Which sucks. However, depending on your risk profile the re-assurance of a hardware solution that lights up the LED might be plenty for you.

I believe the one for iPad is a bit confusing, as I think it has software invoked. Namely, when a case closes and iPad goes to sleep I think the OS tells the hardware to physically disconnect. (You’ll notice the wording is a bit different for Macs.)

AFAIK there's no official Apple document. Would you accept the recollection of an anonymous former Apple engineer writing to a fairly popular blog? /s

https://daringfireball.net/2019/02/on_covering_webcams

> All cameras after that one were different: The hardware team tied the LED to a hardware signal from the sensor: If the (I believe) vertical sync was active, the LED would light up. There is NO firmware control to disable/enable the LED. The actual firmware is indeed flashable, but the part is not a generic part and there are mechanisms in place to verify the image being flashed. […]

What if the LED burns out? Is there any redundancy?

I'm not sure I follow. If the LED burns out you're implying the camera would no longer work? I imagine they'd replace the whole camera module. I saw one for an older model on ifixit for $30. I'd probably try and snag one scrap. I'm not sure how often it comes up.

They mean how do we get warned that the camera is active if the LED burns out?

I have no idea, but I would imagine if the LED is burned out the camera would not work.

I’ll accept it, but not bet my life on it :)

Would be nice if they explained how the hardware worked.

Hardware is not free from bugs. Ask any hardware manufacturer!

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