Hacking Voice Assistants with Ultrasonic Waves

I previously wrote about hacking voice assistants with lasers. Turns you can do much the same thing with ultrasonic waves:

Voice assistants—the demo targeted Siri, Google Assistant, and Bixby—are designed to respond when they detect the owner’s voice after noticing a trigger phrase such as ‘Ok, Google’.

Ultimately, commands are just sound waves, which other researchers have already shown can be emulated using ultrasonic waves which humans can’t hear, providing an attacker has a line of sight on the device and the distance is short.

What SurfingAttack adds to this is the ability to send the ultrasonic commands through a solid glass or wood table on which the smartphone was sitting using a circular piezoelectric disc connected to its underside.

Although the distance was only 43cm (17 inches), hiding the disc under a surface represents a more plausible, easier-to-conceal attack method than previous techniques.

Research paper. Demonstration video.

Posted on March 23, 2020 at 6:19 AM18 Comments


La Abeja March 23, 2020 11:40 AM

Voice assistants — the demo targeted Siri, Google Assistant, and Bixby — are designed …

I don’t like the crowd that designs this stuff. It’s Silicon Valley, and it’s definitely not open source.

Ultimately, commands are just sound waves, …

That’s quite an attitude, especially when they’ve got military contracts etc. after they’ve banned guns for us on the pretext of Congress’ arbitrary and absolute authority to regulate “interstate commerce.”

Phaete March 23, 2020 12:43 PM

Only the fact that the wave spectrum is like magic to most makes this news.
So it is heavy on the circumstances and very light on the obvious physics of why this works and how sound sensors (microphones) work so they can be easily fooled.

In the end everything can be hacked/fooled/circumvented etc, this is just too easy, far too many attack angles to fool a analog wave detector (microphone again)

Just the beauty of what the wave spectrum is and the range of what waves can do is magnificent. I encourage everyone who to read up on it on their favourite info sites (not gonna give you any, you know where to get the ones you like)

lurker March 23, 2020 2:18 PM

The banality of “voice operated assistants” was revealed to me when the resources of a Starship were required to make a cup of Earl Gray tea. OK that was fiction, but the truth has only gotten stranger since then…

La Abeja March 23, 2020 3:09 PM


So it is heavy on the circumstances and very light on the obvious physics of why this works and how sound sensors (microphones) work so they can be easily fooled.

They’re the experts and we’re not qualified to peer-review them.

It’s all hats off, hold the chairs, doors open for the ladies, please be sure to get your hand stamped or a non-tear bracelet when you pay your conference admittance fee, so the bosses won’t need to have you escorted off the property etc.

uh, Mike March 23, 2020 4:57 PM

Paranoia here. Has anyone else’s Macbook been making noise like disk chatter, in the left speaker, when there’s only an SSD? The Internet says, “coil noise.” Yeah, right.

Clive Robinson March 23, 2020 5:11 PM

@ lurker,

when the resources of a Starship were required to make a cup of Earl Gray tea.

Not quite you forgot the word that caused the most problems “Hot”.

The Starship resources were required not to make the tea, simple mechanics would do that. But to work out what “Hot” ment to the individual. Obviously it was somewhere between 0-100C but where exactly, not just for the initial steeping[1] but for the man to drink at that time and the mood he was in. That’s why “real human servers who know their customers well” will always find a place in any universe real or not 😉

[1] You will hear many people say that the pot has to be “warmed” and the water “just off of the boil”, neither is true. If you put “tea leaf” –not powder– into cold water and leave it for a long enough period you will get a lighter flavour with more of the floral top notes that when drunk cold has a pleasant flavour unlike hot brewed leaf tea gone cold. The chemistry and physics of flavours is a complex subject, and woe betide the person in search of “the perfect cup of tea” as another star traveler found when “thumbing a lift”, some ships computers are just not upto the job no matter how genuine their people personalities are, which is why people related to Marvin 😉

Phaete March 23, 2020 5:42 PM


In which case it was good that Earl Gray was specified, green or white tea has different optimal steep temps and times.
The bergamot essence could be easily accounted for when the pollutants were known, which i assume a are not outside the capabilities.
Same goes for the water itself, calcium and whatyouhavenots in there.
Please elucidate clive, i am yearning for your viewpoint of the horizon on these inflicted quarantine days.
Even more so on the EM spectrum, i hope you are feeling well.

La Abeja March 23, 2020 6:12 PM

@Clive, Phaete

Earl Gray … tea … bergamot essence …

I was looking at it on the grocery store shelf one day. There were other varieties, including “Lady Grey” and “Double Bergamot Earl Grey” and I was suddenly approached by a crowd of men with a stricken look on their faces.

“I didn’t know Earl Grey was old,” one of them said to me. I don’t know exactly what he meant by that, but where I’m from, when Cártel de Jalisco Nueva Generación calls something old, you just throw it out, stay away from it, and don’t buy any more of it.

I was forced to flee that town for my life when they took over from Cártel de Sinaloa and the Bloods, and the Portland Police force went 100% Crip.

Achille Papin March 23, 2020 6:28 PM

Re. le thé, and why I don’t travel on spaceships

Den enda perfekta kopp te är den som är gjord i en gammal silver tekanna av din mormor.

Achille Papin March 23, 2020 10:46 PM


Well, if you must travel that way, the catalogue has a nice spaceship section, after the kitchen pages.

Erdem Memisyazici March 24, 2020 11:20 PM

Unfortunately unless you are willing to put down a few hundred dollars, no device records audio above the 20khz range. I actually purchased a microphone to see the audio spectrum in my house near the 40khz range presumably a neighbor deployed to map my house. I found that there is a constant signal exactly at 40khz radiating all the way to my mailbox. Source unknown given I need to triangulate to find it. No normal microphone would lead me to this conclusion. The point is, there is nothing like mechanical waves to give you a 3 dimensional picture of a site like high frequency waves. Next best option is radio active where you damage your target just to see it.

Clive Robinson March 25, 2020 6:01 AM

@ Phaete,

Please elucidate clive, i am yearning for your viewpoint of the horizon on these inflicted quarantine days.
Even more so on the EM spectrum, i hope you are feeling well.

The good news is that the two people I was worried about on the Diamond Princess are safe and well. However my son and his mother are now in 14day quarantine as she being a healthcare worker in very close proximity to one of the few infectious wards in London has all the symptoms. But she like most of her key worker colleagues in her department have been told to “stay at home” thus won’t be tested (so won’t count) on the UK numbers[1]…

But I must apologize for my late reply, I’ve kind of been busy looking at research papers as we have no real experience to fall back on as the virus is “novel”.

However even this old dog gets to learn new tricks. I was vaguely aware from a head injury back in late 2000 that upper respiritory infections could effect your ability to “smell” and as a consequence “taste”. This viral anosmia is a little more general than I realized. Apparently Ear, Nose and Throat (ENT) sprcialists have seen a significant up swing in cases of what appeared to be viral anosmia. Turns out it’s another likely indicator of COVID-19, as those that got tested showed up as having the virus. Importantly most did not go on and show other symptoms, even though they would have been “shedding virus” thus infectious[2].

So if people start loosing their sense of smell or taste for no other apparent reason, it’s probably better to keep your self issolated from others so you don’t become a “super spreader”.

Other notes of interest, from European data it appears that,

1, Twice the number of men.
2, BMI over ~25 (~7 in 10 cases).

Are showing up in those requiring hospital support and getting more serious complications.

These two may not be unrelated. Men tend more to “internal” and belly fat than women do. Internal fat reduces the ability for you to take deep breaths in normal times, so it’s certainly not going to help when you have a respiritory disease. Speaking of which men get more non-communicable respiritory diseases than women do, and yes they do tend to snore more and get the likes of sleep apnea.

As for me, well I appear to be well, but as I had contact with my son and his mum during their possibly infectious stages, I’ve decided “to be nice to others” and self quarantine for now. Which means I will probably get that “Issolate your self for 17weeks” notice from the UK Gov that they are sending out to the old, the infirm, and those cantankerous types with comorbidities (of which I am apparently one according to the pill and plunger pushers, why they don’t just say “lovable rouge” or “old git” I don’t know 😉

Any way I hope this missive finds you both hale and hearty and I hope you and all others stay that way. Just remember to practice saying “Hugger hoft” loudly in the mirror each day and repeat as necessary when people come into your new expanded “personal space”. If you are not sure stick your arm out straight to wards them waving your walking stick, if it hits them they are “to close” 0:)

Remember that one of the best pieces of advice is “always be chearful and helpful to others”, but apparently not for the “kill joys”. For it is they that have decided I’m not supposed to hand out that useful walking stick advice, even though it is a realy good ready reckoner for the 6ft seperation they insist on. It realy is like them to take away what little fun you can find in an otherwise gloomy situation. Oh apparently my second suggestion of “In that case I guess you could always stick a yellow flashing light on your head” was equally not well received, maybe they thought I was being personal (the third suggestion I was thinking certainly was[3] 😉

[1] As for what are very clearly “massaged figures” in the UK, it appears the political arm of the NHS the Department of Health has missed a trick. It they test her and her colleagues as the come back, it takes the “clear figures” up in the “tested” numbers, but they also kind of become eligable to be slipped in the “recovered” figures as well… Maybe that’s one statistical trick they know they could not get away with even in a relatively short time.

[2] In the not to distant past we would have used the word “contagious” not “infectious”, contagion being felt to be a better word for community spreading diseases (atleast better than the older plague). I wonder if the old word will come back…

[3] It involved redeploying an otherwise normally recumbrant member of the genus anatidae for a proceadure that PR experise of the medical variety might be required.

Phaete March 26, 2020 4:20 AM


I am glad to hear from you and hope all will remain ok for quite some time longer for you and your family.

As always, you have given me something to read about, viral anosmia is quite interesting, far more then the current things on my mind.
As a broad shouldered 2m03 male, i have no difficulty with the social distancing.
Most people distance themselves from me without them even being aware of it, this has been since my body matured. A combination of a “Hmmm” and a growl is enough for any unwary.

Good tidings to you and everyone you love.
Time to get your favourite Pratchett novel out of that bookcase (I have a bookcase full, and i’m pretty sure you have as well somewhere)

Phaete March 26, 2020 12:26 PM

@La Abeja

I was looking at it on the grocery store shelf one day … but where I’m from, when Cártel de Jalisco Nueva Generación calls something old

My detector is detecting the special flavour of humour associated with Aspergers, is my detector wrong?

In any case it is tickling mine.

La Abeja March 26, 2020 5:04 PM


Aspergers, is my detector wrong? In any case it is tickling mine.

That is very, very wrong. Such esteemed doctors and educated gentlemen “of the district” who proffer such false and injurious medical diagnoses on such an arbitrary and involuntary basis for the gratification of their own flesh, must be punished out of such vicious practices, punished into compliance with every possible law, rule, and regulation applicable to the field of medicine, and further punished into a proper respect for our Constitutional, civil, and human rights.




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