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Comment by dataker | Hacker News Reader

If anyone is exploiting my system, microphone would be my top priority. Getting image doesn't really tell as much as listening to what, how and when you talk.

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It establishes that you were there at a particular time. A jury or secret tribunal would probably believe a picture that they can see for themselves easier than an expert's voice print testimony.

You can also extrapolate a fairly decent image from the microphone, sort of like a make-shift SONAR.

From multiple microphones, perhaps, but from a single microphone? Seems unlikely.

You have an array of microphones in your phone alone, not to mention the speakers, which are just low-fi mics. But in any case, you can do it with one microphone.

E.g. http://fab.cba.mit.edu/classes/862.13/students/brandon/index...

http://www.extremetech.com/computing/128735-microsoft-create...

That first technique A) is very audibly noticeable B) requires you to put the laptop on a chair and wheel it around the room to make up for the fact that you only have a single microphone.

The second technique basically only understands gestures.

I wouldn't be at all worried about this in the wild...

Someone actually did it to China's PLA Unit 61398 using a technique similar to this: http://www.gizmag.com/microphone-room-mapping-epfl/27985/, so I'd say it's worth worrying about in the wild.

Its unlikely the speakers can be used as microphones, as they will be wired up to D/A converters and not D/A converters.

You can produce a depth map from a single lens camera by manipulating the flash across multiple captured images. Similar results could be achieved with a single microphone if the device also has speakers capable of producing sound at certain frequencies.

The mic would also record the sound of keystrokes.

Where is the microphone on a MBP?

Varies from model to model, but on my 15" Retina MBP, it's tucked in under the left speaker grille, near the Tab key. Pull up some software that shows you a live mic level (e.g. System Preferences -> Sound -> Input tab), and rub your finger gently over the grille, and you can usually tell roughly where it is by the spike in input volume.

If you're wondering about blocking it off, though, that's much harder than the camera. You'd basically have to open the laptop and unsolder the mic capsule -- or mount a little white noise generator right over the mic, but then you can't close your laptop. :-)

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