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Comment by jwr | Hacker News Reader

Every microphone in every powered device must be considered as listening if you are serious about security at all.

So what if the panel actually even disabled the mic preamp on the board? You could have a program/virus/trojan that silently re-enabled it behind your back, without you knowing. So I'd say this is nothing to be concerned about, because every device you own potentially "listens" with its microphones all the time.

The advice with plugging a jack into the line-in port is good -- if you're sure your hardware hasn't been tampered with, this should physically disconnect the microphone.

Obviously if you're really worried about your computer listening, you should rip it open and physically cut the microphone connection.

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> "if you're sure your hardware hasn't been tampered with, this should physically disconnect the microphone."

Why so? Most soundcards merely detect an impedance change and flick a bit to switch from internal microphone to line-in but you can have full control of that bit by software. That's actually what the prefpane does: even with something plugged in the line in, one can switch back to the internal microphone as a source. (EDIT: apparently it goes hidden on new hardware revisions but the functionality is there, just boot into Linux and do some poking on the soundcard to see what's really available)

You can still insert a barrel jack, this time with 4 rings instead of 3 at which point the microphone is disabled.

For example, Apple headphones for your iPhone can be plugged in and used for that purpose...

Only if you cut the microphone off, of course. :)

You can buy a 4 ring 1/8" plug adaptor for headphones. Some of these adaptors come with no mic.

I believe the LED that tells you your MacBook's camera is on is hard-wired into the motherboard, for the very purpose of making it impossible to covertly enable the camera via software. A similar approach could be used for a mic.

This is not true. The software Prey (which is designed to spy on people who have computers that have been stolen) takes covert photos and sends them without activating the light.

I just installed Prey, marked my MacBook Pro as missing, waited, and the light definitely did come on - albeit for around two seconds - while taking the webcam picture.

There is no way in software to disable that LED.

I did this test as well when I first heard about Prey. The first couple times when I knew the picture was going to be taken I did not see the light.

The reason is because we can only focus on one thing at a time. While waiting for the picture I was casually browsing the net -- probably reading HN -- and only periodically looking up to watch the light. I assumed a light source would catch my peripheral vision. It had not. For the third test I stared at the camera with an unbroken focus. Sure enough, the light turned on as expected.

Net: I could not see the light unless /I was looking at the camera/. It's a side effect of how the mind works and processes information. It's also important to keep this fact in mind when building interfaces: don't alert users in places they aren't looking. They won't see it no matter how red or many sparkles you add. :)

And if you're really really worried, you should rip out the speakers too. Just in case someone's wired them up to work in reverse...

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