
Detecting Screen Content via Remote Acoustic Side Channels - nfrankel
https://www.cs.tau.ac.il/~tromer/synesthesia/
======
John_KZ
Although this method can be used for de-anonymization and fingerprinting, you
can't fully reconstruct the screen contents from such a low bandwidth signal.

If your private spaces are bugged with microphones or cameras (ie most mobile
devices, home audio "assistants", smart TVs, untrusted software etc) expect
the owner of the sensor to do the best in their abilities to spy on you.

Ultrasonic ad fingerprinting is another interesting way your home spies can
communicate with each other.[1]

[1] [https://arstechnica.com/tech-policy/2015/11/beware-of-ads-
th...](https://arstechnica.com/tech-policy/2015/11/beware-of-ads-that-use-
inaudible-sound-to-link-your-phone-tv-tablet-and-pc/)

------
rocqua
> We assume that the attacker knows the content displayed on the attacked
> monitor, except for the textual letters. This assumption holds in many
> cases, for example, when the victim is filling a form on a known website. We
> also assume that the font is monospace and sufficiently large. The requisite
> size of the text depends on the granularity of the leak, which changes among
> different monitors. Another assumption is, again, that the screen is in
> portrait layout.

They go on to state that in their proof of concept they had 3-6 letter word in
black against a white background. They recorded audio for 5 seconds, and the
letters were 175 px wide using a monospace font.

Note that they do mention they expect that any background could work, as long
as it is fixed and you can train your model on that background.

My point being, this is far from a practical way to read what is on screen.

~~~
ggggtez
I think it's better to treat it as a proof of concept attack. It's more just
to say: hey this type of thing is possible, maybe with better equipment and
more research.

~~~
ttul
Basically, with enough money (read: NSA), you can read anyone’s monitor.

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chupasaurus
I enjoy that nobody knows what the Van Eck phreaking[0] is. It works, but to
get a good picture the gear is quite large to carry unnoticed.

[0][https://en.wikipedia.org/wiki/Van_Eck_phreaking](https://en.wikipedia.org/wiki/Van_Eck_phreaking)

~~~
John_KZ
I assume it's not mentioned because everyone knows it. It's very old news.

~~~
jwilk
But it is mentioned in the article (Q7).

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demomode
IIRC this is what "Tempest for Eliza" was for CRTs

[http://www.erikyyy.de/tempest/](http://www.erikyyy.de/tempest/)

~~~
jwilk
It doesn't have to be CRT. LCD screen connected via VGA works too.

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userbinator
In a less paranoic way, there's this related item:
[https://news.ycombinator.com/item?id=8862689](https://news.ycombinator.com/item?id=8862689)

...which evolved from
[https://news.ycombinator.com/item?id=8856829](https://news.ycombinator.com/item?id=8856829)

------
eb0la
It reminds me Tempest
([https://en.m.wikipedia.org/wiki/Tempest_(codename)](https://en.m.wikipedia.org/wiki/Tempest_\(codename\))
).

This time they are exploiting information leak that goes to unshielded
speakers and can be recorded and replayed easily.

Very clever.

------
WillKirkby
I'm reminded of this DEF CON talk from 4 years ago detailing a similar
technique:
[https://www.youtube.com/watch?v=5N1C3WB8c0o](https://www.youtube.com/watch?v=5N1C3WB8c0o)

------
DoctorOetker
I've noticed this a few years ago, after reading some psychophysics papers, I
was generating some pattern images based on what I read, when my monitor
started emitting tunes (not by radio emissions), I suspect piezo effect in
some capacitor. I instantly realized my monitor could be intercepted
accoustically...

~~~
DoctorOetker
In my case the monitor was an 1080p LCD panel without speakers...

