The T2 chip probably also acts as a controller for a lot of the builtin sensors, including the microphone and lid closed switch. As a result, adding a feature to turn off the microphone when the lid is closed becomes trivial. Basically just add a logic gate between the two.

This is just the way people design circuits these days, because it’s easier and cheaper. A single µC with a few GPIOs, rather than a bunch of logic chips scattered around the board.

The goal is to make this so it cannot be overridden in software. By designing hard-coded logic in a chip that already exists, you can get the same level of security for essentially zero cost.

And if an attacker is able to connect a chip programmer on your motherboard, you have a totally different threat model and bigger problems to worry about.

Have you ever seen a MacBook from the last 10 years? There are no physical switches, it's an hall sensor that works with the magnets that keep the thing closed.

“This disconnect is implemented in hardware alone, and therefore prevents any software, even with root or kernel privileges in macOS, and even the software on the T2 chip, from engaging the microphone when the lid is closed,” said the support guide.

So in this respect, there's no difference between the T2 chip cutoff and a physical switch... except that there could still be a backdoor in the T2 chip cutoff that Apple hasn't admitted to.

I could credentialize in multimonitor usage (I have before), but now I'm getting used to something that's incompatible with portability.

Not to mention it would make the case of the computer microphonic — bump it hard enough and that’ll be transmitted through the reed relay.

Nothing to break, zero attack surface, what's not to like?

But if you're so against moving parts, a hall sensor and a transistor would achieve the same result.

At least with the switch if the mic doesn't work you just check for magnets around it and that's it.

The chip provides a hardware disconnect for the microphone, just like your idea. Except it's baked into the silicon instead of an additional large part in the body of the computer.

Regardless, if your attack model is "T2 chip is compromised", all bets are off. Worrying about the microphone would be the absolute least of your concerns. All your local and iCloud data can now be decrypted, your 2FA is compromised, so on and so forth.

The T2 chip and Secure Enclave provide the strongest security guarantees in today's computers and mobile devices respectively. I'm not worried about a compromise of the T2 chip, to be honest.

If someone can physically modify your laptop, you've already been hacked, T2 chip or not.

if your attack model is "T2 chip is compromised"

I think the more realistic attack model is "Apple enables the undocumented 'turn on mic while closed' feature that it was required to add through a national security letter that they can't talk about."

And then that secret hack is either discovered (or stolen) by other government.

Doing it on a chip sounds more reliable than adding a moving part.

The point (it seems) of the T2 chip is that it's isolated from the main system and has far fewer opportunities for exploitation, while leveraging efforts already expended for the iPhone. In my mind the eventual goal of the T1 / T2 etc chip line will be to do everything for a Mac that an iPhone does—storage, webcam control and encoding, audio in/out, fingerprint reader, sensors, battery monitoring, power management etc—and then expose it all to the main system en masse.

Is it easier the "turn off" signal from the T2 chip to each device to be turned off than it is to route the "turn off" signal from the lid closed switch/sensor to each device. Why does it have to pass through the T2 chip first?

If not, then you’re right it would be exactly the same.

People expect their computers not to listen to them when not actively using the mic. Your switch is the program that records you, a second is redundant and confusing.

Putting this functionality into a computer chip is ridiculous and unnecessary partially because there's no clear way for ordinary non-technical users to control that, and partially because this suggests that software (as I presume the software on this new chip will be alterable by Apple) can still affect whether the mic is hot. The headline "Apple's T2 chip will prevent hackers from eavesdropping on your microphone" should probably be interpreted to mean that Apple won't be prevented from listening in.

Camera access and wireless network access should also be physically disconnectable via a simple user-controlled piece of hardware which electrically disconnecting the on-board webcam and wireless network device from the rest of the system -- a slider or rocker switch. This too is something I understand Librem laptops offer but is uncommon elsewhere.

Now, if you trust Apple, the T2 chip is perfectly secure for this use case. Apple claims this serves as a hardware disconnect baked into the silicon, in which case it is no different from a mechanical switch.

Finally, the whole argument about user control over various security features is interesting. I will say that Apple has, better than any other manufacturer, struck almost perfectly the balance between security and usability. Apple's software/hardware security does its job, does it well, and gets out of your way. Including 20 different hardware switches and 150 different security settings that mean nothing to the average user would not be in their design language.

It's all about your threat model. Perhaps yours is a bit too severe to use traditional consumer devices.

If Apple distributed free software trusting Apple wouldn't enter into the discussion. We could inspect what Apple distributed, we'd be allowed to change what we don't like about the software Apple distributed to us, and we could distribute improved versions of that software to help others. No need to buy into uninspectable code we're not allowed to change or distribute further.

And the answer to the question you didn't answer which the original poster asked -- do you need a chip to do this task -- remains "no". Purism's hardware is proof by existence. With Purism's hardware switch there's no software involved to accomplish this feature and they (as far as I know) distribute a free software distro called "PureOS" (a GNU/Linux system) which also happens to have earned an FSF-approved distro entry.

Seriously, putting cameras and mics in every device and then creating web browsers which potentially have access to them at all times? Yeah, I'm most worried about what happens when I close the lid.

Any bug or future exploit negates this feature.

I have the feeling this was just done because it was possible and then the marketing team found out about it and decided to make a big deal out of it.

Words don't describe how delusional this is.