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Comment by asax | Hacker News Reader

Why cover the audio mic jack?

Check out the last paragraph here: https://www.wired.com/2014/03/webcams-mics/

> Muting the mic won’t work, since it’s possible for an intruder to unmute it. Your best defense is probably to insert a dummy plug into the microphone jack to prevent sound from being picked up by the internal mic. You can create a dummy plug by simply cutting off the unneeded portion of an old microphone plug. This won’t prevent someone from listening to your conversations when you need the mic, such as when using Skype, but it will at least thwart them from using the microphone on their own without you knowing.

The question stands, why tape the headphone jack? The microphone is not inside the headphone jack.

On some newer laptops, the microphone and headphone ports are combined, so the headphone jack is also the microphone jack. This makes it work with in-line microphones that are popular with most cell phones.

I don't understand what he hopes to accomplish by taping the jack though; it's not like it does anything without something plugged into it.

Put a dummy plug in there and seal with tape?

But that's not where the microphone is (think about it, a microphone stuck down a port wouldn't work well at all).

Right, but having a dummy plug will cause the vast majority of laptops to disable their built-in microphones and instead listen to whatever you plugged in. (In the case of a dummy, this would result in a dead line.)

The idea is to fool the system into having no physical microphone, and even a hacker/malware that compromises the operating system is going to have a hard time dealing with whatever soundcard firmware is responsible for making that switch in the hardware.

On many older devices the signal from the internal microphone is routed through the jack, just like the speakers often connected through the headphone jack. Plugging a device in physically breaks the connection to the mic/speakers in those cases.

That does not apply to most modern computers though, and especially not anything with a four-pin combo jack (including that Macbook). Those have to be able to handle situations where normal headphones are plugged in and the internal mic is still being used, so the mic switching is entirely software on these.

Headphone/speaker switching may be in hardware, but a lot of laptops I've used under Linux allowed me to treat the headphone jack as an entirely separate audio device. I suspect the Macbook would allow the same, though I don't have a new enough one available to test. Mine's an '08 model that Sierra finally EoLed.

Especially odd since it's a retina Macbook Pro, which has a single shared audio in/out jack, which means no use of headphone / external speaker either.

BT could be an easier on/off alternative in that case.

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