More Android phones than ever are covertly listening for inaudible sounds in ads

Almost a year after app developer SilverPush vowed to kill its privacy-threatening software that used inaudible sound embedded into TV commercials to covertly track phone users, the technology is more popular than ever, with more than 200 Android apps that have been downloaded millions of times from the official Google Play market, according to a recently published research paper.

https://arstechnica.com