
Using Ultrasonic Beacons to Track Users - kungfudoi
https://www.schneier.com/blog/archives/2017/05/using_ultrasoni.html
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ArchD
Is there a way to distinguish permission to use the microphone in the
foreground vs in the background? AFAIK on Android, no such distinction is
made. Many apps have legitimate reasons for using the microphone while in the
foreground, but very few in the background.

If there were a simple way to allow foreground use but deny background use of
the microphone, a lot of offending apps would be neutered, but I'm not holding
my breath for Google to change this, just like I'm not holding my breath for
them to allow apps to be silently denied permission by being supplied with
fake data (e.g. empty image for camera) so that they cannot refuse to run if
denied permission.

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mikeash
Apple doesn't make this distinction either. However, they show a BRIGHT RED
BAR at the top of the screen any time an app is using the microphone in the
background, so it never happens without your knowledge. Seems like Google
should at least do that, and letting people block access in the background
would be great too.

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kakarot
I have been following the progress of this tech for a few years now. People
used to take me for a kook but I wish I didn't have a reason to say "I told
you so." This is downright scary.

Having trouble finding this list of 234 compromised android apps or any such
list. Could anyone point me in the right direction? I would be very sad if my
minesweeper app has been listening to ads.

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lucaspiller
Why use ultrasonic beacons instead of cameras and image recognition to track
where people walk? It seems like that would be more effective as you don't
need customers to have a certain phone, and a certain app, and you probably
already have CCTV blanketing your store (at least in Europe).

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gene-h
Perhaps one could prevent this by restricting said apps from using any
frequencies above a certain bound.

