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Headphones can be hijacked to surreptitiously record audio

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Re: Headphones can be hijacked to surreptitiously record audio

#131

Post by toomanybeersies »

ptaipale wrote: post #117
telekid wrote: post #115

Earlier quoted context omitted.

How do you dial a zero? Edit: Just realized why a zero is in the '10' position on a rotary phone. Huh.

Yes, except in the Swedish phones, where the numbering starts from 0. So dialing 0 would make 1 pulse, dialing 1 would make 2 pulses, and dialing 9 would make 10 pulses.

And New Zealand, where it was like Sweden, but backwards. 0 made 10 pulses, 1 made 9 pulses, and dialing 9 would make 1 pulse.

This is why the emergency number in NZ is 111, we had equipment from the UK, where the number was 999.

As to why it was backwards, I have no idea.

Re: Headphones can be hijacked to surreptitiously record audio

#132

Post by toomanybeersies »

mathiasben wrote: post #109
bcheung wrote: post #83

Here's a neat party trick for you. I had a MacGyver moment in the past where I made a phone call with only are pair of old earbuds and a phone cord (no switches, no dial pad). A speaker is basically the same thing as a microphone in reverse. Normally it takes an electrical signal to move a physical element that creates the sound waves. But you can also move the element and it will generate an electrical signal. To di…

I've used this before in a pinch too, speaker as a microphone in reverse. that got me wondering... would it be possible to use the same principle with another type of listening device. Focusing a laser beam on a window allows you to hear a conversation in the room. so could the same principle be applied and allow a laser beam to transmit audio?

You can use a laser to transmit audio to a LDR or a light sensitive transistor/diode, which can then be used to run a speaker (with a battery attached). Essentially fibre optics through the air.

I did it once, the quality was rather lacking, since it used amplitude modulation instead of frequency modulation.

Here's an instructable on it: http://www.instructables.com/id/How-to-Send-Sound-using-a-La...

It's not quite what you're asking, but it's probably the closest you can feasibly get. I'm fairly sure that's also the way that laser microphones work as well.

Re: Headphones can be hijacked to surreptitiously record audio

#133

Post by [deleted] »

toomanybeersies wrote: post #131
ptaipale wrote: post #117

Earlier quoted context omitted.

Yes, except in the Swedish phones, where the numbering starts from 0. So dialing 0 would make 1 pulse, dialing 1 would make 2 pulses, and dialing 9 would make 10 pulses.

And New Zealand, where it was like Sweden, but backwards. 0 made 10 pulses, 1 made 9 pulses, and dialing 9 would make 1 pulse. This is why the emergency number in NZ is 111, we had equipment from the UK, where the number was 999. As to why it was backwards, I have no idea.

[deleted]

Re: Headphones can be hijacked to surreptitiously record audio

#134

Post by christoph »

toomanybeersies wrote: post #131
ptaipale wrote: post #117

Earlier quoted context omitted.

Yes, except in the Swedish phones, where the numbering starts from 0. So dialing 0 would make 1 pulse, dialing 1 would make 2 pulses, and dialing 9 would make 10 pulses.

And New Zealand, where it was like Sweden, but backwards. 0 made 10 pulses, 1 made 9 pulses, and dialing 9 would make 1 pulse. This is why the emergency number in NZ is 111, we had equipment from the UK, where the number was 999. As to why it was backwards, I have no idea.

112 still works as an emergency number in the U.K. to this day.

Re: Headphones can be hijacked to surreptitiously record audio

#135

Post by Johnny555 »

anigbrowl wrote: post #94
bcheung wrote: post #83

Here's a neat party trick for you. I had a MacGyver moment in the past where I made a phone call with only are pair of old earbuds and a phone cord (no switches, no dial pad). A speaker is basically the same thing as a microphone in reverse. Normally it takes an electrical signal to move a physical element that creates the sound waves. But you can also move the element and it will generate an electrical signal. To di…

You don't even need to disconnect the ear bud, just tap it. The voltage pulse from an audio signal is sufficient. Back in the days of rotary phones I used to show off how to dial numbers by simply tapping the receiver on the table.

That doesn't seem to work - I have a POTS line here, and no amount of tapping or striking the phone receiver on a surface is the equivalent of dialing (I tried the phone itself and my headset microphone). Perhaps a local VoIP ATA works that way, but my Telco does not. And I'm not surprised, there's a big difference between detecting an audio signal and detecting a local loop interruption through 18,000 feet of copper.

Re: Headphones can be hijacked to surreptitiously record audio

#136

Post by Johnny555 »

ChuckMcM wrote: post #93
IshKebab wrote: post #57

The bit you want to know: > Their malware uses a little-known feature of RealTek audio codec chips to silently “retask” the computer’s output channel as an input channel

Not a "little known" feature, it is the feature that lets you plug your head phones into any of the 6 jacks that it looks like it fits in on the back of your computer and the little pop up says "Are those headphones you just plugged in?" you say yes and that jack is retasked as as headphone jack even though it was the subwoofer output according to the legend on the computer plate. Its a "feature" that they have sold…

Do you get a corresponding "Is that a speaker you just plugged in?" popup if you plug a speaker into the microphone port?

How does the computer know whether you've plugged a speaker or a mic into the port?

Re: Headphones can be hijacked to surreptitiously record audio

#137

Post by justinclift »

janci wrote: post #76
justinclift wrote: post #71

Earlier quoted context omitted.

It seems like something that would work for built-in speakers too. They're driven by the same audio codec chips (eg realtek), but wired directly instead of through an external socket.

I think the opposite. Speakers are driven by an amplifier that will not let the audio in reverse, even if the soundcard output was switched to act as an input.

Interesting point, hadn't considered that.

Sounds like it'll be one of those "implementation dependent" things then, and someone into this kind of thing should probably investigate.

Re: Headphones can be hijacked to surreptitiously record audio

#138

Post by markrages »

Johnny555 wrote: post #136
ChuckMcM wrote: post #93

Earlier quoted context omitted.

Not a "little known" feature, it is the feature that lets you plug your head phones into any of the 6 jacks that it looks like it fits in on the back of your computer and the little pop up says "Are those headphones you just plugged in?" you say yes and that jack is retasked as as headphone jack even though it was the subwoofer output according to the legend on the computer plate. Its a "feature" that they have sold…

Do you get a corresponding "Is that a speaker you just plugged in?" popup if you plug a speaker into the microphone port? How does the computer know whether you've plugged a speaker or a mic into the port?

Microphones have a higher impedance than speakers. A moderately clever circuit can differentiate the two.

Re: Headphones can be hijacked to surreptitiously record audio

#139

Post by haimez »

ptaipale wrote: post #117
telekid wrote: post #115

Earlier quoted context omitted.

How do you dial a zero? Edit: Just realized why a zero is in the '10' position on a rotary phone. Huh.

Yes, except in the Swedish phones, where the numbering starts from 0. So dialing 0 would make 1 pulse, dialing 1 would make 2 pulses, and dialing 9 would make 10 pulses.

This is how ISO happened...

Re: Headphones can be hijacked to surreptitiously record audio

#140

Post by knodi123 »

mark-r wrote: post #10
chias wrote: post #7

Earlier quoted context omitted.

The author of the article intended to write "output-only". But even this is not quite right: it's by definition not an input-only jack, but rather a jack capable of both input and output (which the user may think is output-only), but that RealTek has quietly switched to input mode as a result of their malware. Really this title is alarmist. Only very specific hardware, and you'd have to not notice the sound stopped.

Most people don't play sounds all day. But this does point to a viable defense, if the headphones are always playing something they can't be used to record.

If you're looking for the most viable defense, how about unplugging your headphones.
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