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Hackers send silent commands to speech recognition systems with ultrasound

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

#61

Post by delinka »

rmonroe wrote: post #30
delinka wrote: post #22

Earlier quoted context omitted.

"...no hardware solution..." There is for new hardware. It's relatively simple to include a couple components on the mic input to filter out ultrasound. There is indeed no hardware fix for anything already manufactured.

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.

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

#62

Post by sangnoir »

arkad wrote: post #23
carlps wrote: post #8

Earlier quoted context omitted.

Except the inaudible sounds are used for marketing purposes. Most companies aren't going to want to just close that door.

I'm genuinely curious - can you share a link how it works please? I've never heard of it.

I know of traditional media ad-tech that uses ultrasound markers embedded in ads to track/verify if the ads were really broadcast as promised (number of times & in the correct time slots.

So the steps are:

1. Inject ultrasound markers into ad during post-production.

2. Have a server with multiple tuner cards to monitor multiple stations, grab the audio.

3. Filter audio on specific ultrasound frequencies, search for the pre-injected patterns.

4. Generate reports.

5. Get paid.

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

#64

Post by kleiba »

krisdol wrote: post #53
maxerickson wrote: post #42

Earlier quoted context omitted.

Unplug Alexa, turn "Hey Siri" off. Schlep to store for Cheerios.

But how will the store acquire all my personal information that way?

By using the same credit card for each purchase.

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

#65

Post by sangnoir »

js8 wrote: post #44
tinus_hn wrote: post #9

Even if the commands are not inaudible it's a security issue if the device performs a dangerous action because someone in the neighborhood said something. The feature is presented as if it only responds to the owner but realistically that distinction doesn't work at all. If you shout 'hey Siri' into the microphone at a large event, a lot of phones are going to respond.

> If you shout 'hey Siri' into the microphone at a large event, a lot of phones are going to respond. Curious - anybody ever tried that?

Burger King had a TV ad[1] that triggered Google Assistant and Google Home ("OK Google, what is the whopper?")

1. https://www.theverge.com/2017/4/12/15277278/google-home-burg...

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

#66

Post by jlrbuellv »

pls2halp wrote: post #15
retSava wrote: post #14

Earlier quoted context omitted.

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

I’m pretty sure that Hey Siri is keyed to the users voice to some extent, so Siri should be safe. Not sure about Google, Cortana, Alexa etc.

"OK Google" on my Pixel is keyed to my voice and can be used to unlock the phone (though I turned that feature off), but I'm not sure if it validates my voice when the phone is already unlocked, or if other google devices like the Home allow this.

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

#67

Post by willvarfar »

The range limitation seems possible to overcome too.

There are directional megaphones that can send sound for hundreds of meters. Directional megaphones send a beam of ultrasound that is focused on the surface where the sound is to be generated, so an attacker may be able to use a directional megaphone to beam the voice commands to the target's vicinity.

Suddenly all kinds of movie plot tricks could be used in heist movies now! Perp uses an air vortex cannon to press a door bell button from a distance and a directional megaphone to talk to in the buzzer and then ... well, easy to get carried away :)

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

#68

Post by shakna »

dingo_bat wrote: post #54
shakna wrote: post #45

Earlier quoted context omitted.

> Only treating signals using human voice range Inter-modulation will let you create something hardware can't tell isn't. Two inaudible sounds, both getting received end up looking like an audible one to the hardware. The harmonic effect described in the article is similar, and damn hard to filter against physically. > For example, commercials could add ultrasounds to know who's watching them Yep, and we're already t…

But if mics can pick it up, human ears will also be able to hear it.

Why? Most microphones have a greater range than your ears do.

Here's a StackOverflow thread [0], exploring what sounds a smartphone can hear, that a human can't.

So, going with interleaving two sounds to make something the mike thinks is audible, when it isn't:

Sound A is at 13khz, Sound B is at 12khz.

Human ear can't receive either, so is unlikely to notice it at all.

But most smartphones can actually pick up those signals, and together, get a signal at probably ---

(Disclaimer: I'd have to investigate further to give a precise, or meaningfully correct answer, but the above outlines the theory).

[0] https://electronics.stackexchange.com/questions/59157/over-w...

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

#69

Post by javra »

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.

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

#70

Post by imglorp »

snarf21 wrote: post #50
tinus_hn wrote: post #9

Even if the commands are not inaudible it's a security issue if the device performs a dangerous action because someone in the neighborhood said something. The feature is presented as if it only responds to the owner but realistically that distinction doesn't work at all. If you shout 'hey Siri' into the microphone at a large event, a lot of phones are going to respond.

There are others issues with out user keyed audio triggers. Stand outside a living room door and yell "Alexa, open the door" and it may open. Even before this finding, there is the ability to embed things in app/game audio or advertisements. This now also lets commands be embedded here as well and not be audible. Soon, we'll have secret commands hidden in songs that try to turn on all your tvs and audio players and s…

Or just trackers.

You TV can emit tones your various devices can pick up, sending back data on what content you're consuming.

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