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Hackers send silent commands to speech recognition systems with ultrasound

techcrunch.com

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Re: Hackers send silent commands to speech recognition systems with ultrasound

#71

Post by vel0city »

delinka wrote: post #61
rmonroe wrote: post #30

Earlier quoted context omitted.

They are taking advantage of nonlinear properties in the microphone system, as described clearly in the article. There is no software filtering to protect against this using classical signal processing. That said, it may be possible to detect the difference between human speech and the ultrasonic trick with a machine learning solution.

The thing is, this is creating harmonic vibrations in the membrane at human speech frequencies. I really don't think you need to go with ML. It seems to me that if you remove the LPF, let the ADC access all the frequencies, then (either in the ADC or in software) detect the harmonics and ignore those with an ultrasound source. Edit: suggest LPF removal.

Wouldn't it go through a bandpass filter to remove the ultrasonics before it makes it to the ADC? I thought that was common with DACs to reduce aliasing issues.

Re: Hackers send silent commands to speech recognition systems with ultrasound

#73

Post by EGreg »

javra wrote: post #69
EGreg wrote: post #59

Can't Alexa, et al simply look for a certain volume and duration in the audible range, which sounds like speech, in order to activate?

I think volume is the key here... The hackers induced harmonics in the audible range but at a volume that was only perceivable by the microphone and not by the bystanders. So to me it seems that it's possible to prevent this by require a higher threshold of volume to activate.

I am just worried the hackers will then make sounds that sound like noise, but at least it will be characteristic and alert the person (maybe).

Re: Hackers send silent commands to speech recognition systems with ultrasound

#76

Post by kazagistar »

retSava wrote: post #14
baldfat wrote: post #3

This is MUCH bigger deal than most understand. This will cost less than $10 to build and their is no hardware solution on phones or Alexia. Phreaking is back.

Yeah, those parts are easily available on Aliexpress in droves. Imagine this in the crowded subway. "hey siri" "show me pictures of CENSORED " "send the first picture to mom" "yes, send it" :S

How about forwarding password reset emails?

Re: Hackers send silent commands to speech recognition systems with ultrasound

#77

Post by delinka »

vel0city wrote: post #71
delinka wrote: post #61

Earlier quoted context omitted.

The thing is, this is creating harmonic vibrations in the membrane at human speech frequencies. I really don't think you need to go with ML. It seems to me that if you remove the LPF, let the ADC access all the frequencies, then (either in the ADC or in software) detect the harmonics and ignore those with an ultrasound source. Edit: suggest LPF removal.

Wouldn't it go through a bandpass filter to remove the ultrasonics before it makes it to the ADC? I thought that was common with DACs to reduce aliasing issues.

Apologies - I was amidst edits when I was called away. I've addressed this by suggesting removal of the LPF.

Re: Hackers send silent commands to speech recognition systems with ultrasound

#78

Post by beager »

narrowtux wrote: post #52
beager wrote: post #33

As the article says, there is a physical presence bar to meet to make this workable now, but I can't not think about clever ways that this could become a "worm" or spread digitally. Infected viral (actually viral!) YouTube videos? Robocalls that you hope go on speakerphone (where the fidelity of the attack signal may be questionable)? Or drive a car with big speakers around a neighborhood? How about a mobile phone bo…

The speakers would have to be able to emit ultrasonic waves. I'm pretty sure that you need special hardware for this. (because the researchers themselves used a special ultrasonic emitter, not the speaker of the phone they used).

Good point. I wouldn't trust that the speaker on a mobile phone has a very good frequency response, but a TV or car stereo might be able to swing it.

Re: Hackers send silent commands to speech recognition systems with ultrasound

#79

Post by parhurs »

Retr0spectrum wrote: post #74

Presumably, you could also broadcast an AM radio signal at just the right frequency that the wires in the microphone pick it up.

This already been demonstrated on headphones[0].

[0] https://www.wired.com/2015/10/this-radio-trick-silently-hack...

Re: Hackers send silent commands to speech recognition systems with ultrasound

#80

Post by athenot »

Using ultrasounds as a side-channel is also used by Cisco's proximity sensors for telepresence units and the new Spark Boards. While on a call on my phone, I can walk into any conference room and swipe to handoff the video call from my phone to the room's telepresence unit, even if my phone is not on wifi (e.g. because I just walked into the building or had wifi turned off). In my experience, this flows much smoother than any wifi– or bluetooth–based pairing.

https://www.cisco.com/c/en/us/products/collaboration-endpoin...

Full disclaimer: I work in that BU.

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