Great Read. It wasn't discussed in the article, but I am curious as to the range/distance such ultra sound signals can travel and be picked up by a cheap smartphone mic, etc...? An example where the answer is relevant would be a smart TV located in another room maybe 30 ft away. Such devices have very low end mic's and stuff. One thing this affirms for me is my desire to keep Java and scripting OFF on my TOR browser. A rooted smartphone with appropriate firewall tech to counter this would likely be the best thing that would be available, for someone in my mid-level skill set. Lacking root I would not trust the publicly available solutions presented. The 3 letters still have control where ROOT is missing. ps - edit: Just had a thought. Wouldn't it be simple to create a jammer of sorts? How about a ultrasound generator sending non-stop signals that would overwhelm any listening device rendering the actual weak signal useless because it cannot be interpreted. Now this would be very simple to build. Just design randomizing parameters for the signal transmitter. Would take virtually no power, you wouldn't hear it, and at this strength it would be fully safe to use. It would be set weak enough to not interfere with neighbors but strong enough to set next to your phone and "kill" the phone mic. How does that sound?
You mean like white noise machine but in ultrasound frequency? Entirely possible. https://www.youtube.com/watch?v=O_jvJzOSwtY
You might find some canine curiosity! I've also felt this technique could be used as an exfiltration mechanism from airgapped computers - infect by usb, then listen to the connected devices in the airspace.
I read the a similar article at ghacks. http://www.ghacks.net/2017/01/06/silverdog-a-sound-firewall-for-chrome/ There is an extension available for chromium base Very informative youtube video as well https://www.youtube.com/watch?v=WW1-xnTIDjQ regards.
So if I turn off my speakers with this prevent the attack? Does this in any way also travel through the router? What if there is another phone downstairs? How far can it reach? Do any addons like noscript or ublock origin block this?