You suddenly remember that you need new tires for your car, and then an hour later, you find tire advertisements popping up everywhere on your phone. Your friend says it's suspicious, while your wife says you're overthinking it.
Here’s the truth: the reality is worse than both possibilities.
In 2024, "404 Media" obtained a leaked presentation from "Cox Media Group," and the giant marketing company was promoting something called "Active Listening," according to a report from the tech advice site "Komando."
The presentation stated that smart devices can "capture intent data in real-time by listening to our conversations." It also listed Google, Amazon, and Facebook as partners.
Google responded by removing "Cox" from its partner program. Amazon denied everything, and "Cox" claimed that these materials were "old."
Researchers at Northeastern University analyzed 17,000 applications on the Android system for covert microphone access. They found not a single app that recorded user audio.
However, the researchers found apps that were secretly taking screenshots of users' phones and sending the images to third parties. One of the apps recorded video of everything displayed on the phone screen, including user messages, browsing history, and passwords.
The sound you can't hear
This technology is called Ultrasonic Cross-Device Tracking.
Companies embed inaudible sound signals, at frequencies above 18 kilohertz—beyond human hearing—into TV ads, websites, and even store speakers.
Your phone silently picks up these signals, then associates itself with your television, laptop, and tablet. Thus, advertisers know that all these devices belong to the same person.
In other words, this technology does not rely on recording the user's voice, but rather on capturing inaudible sound signals broadcast within certain ads or public spaces. When the phone picks up these signals, advertising companies can link it to other devices used by the same person, helping them build a more accurate profile of their interests and behaviors.
Researchers found that 234 Android applications were quietly listening for these ultrasonic signals without users' knowledge. The apps did not need a Wi-Fi connection, only microphone access permission. That permission you granted three years ago to a flashlight app, for example, was like an open door.
Add to that your geographical location data, browsing history, loyalty card purchases, and the Facebook Pixel tool that tracks you across millions of websites. All of this data aggregates to create a highly precise profile, making you feel as if someone is listening in.
How to prevent it
To prevent such silent tracking, you should review microphone permissions, turn off personalized ads, and stop your smart TV from snitching on you, as well as your Alexa assistant.
1- Microphone permissions
On iPhone: Settings > Privacy & Security > Microphone. Turn off the permission for every app that doesn’t urgently need it.
On Android: Settings > Privacy > Permission Manager > Microphone. Follow the same steps. If a calculator app has permission to access the microphone, that's a huge red flag.
2- Turn off personalized ads
On iPhone: Settings > Privacy & Security > Apple Advertising, then disable the Personalized Ads option.
On Android: Settings > Privacy > Ads > Delete Advertising ID. This won't stop all ads, but it will prevent ads that know you searched for "knee pain" at 2 AM.
3- Stop your smart TV from snitching on you
On Samsung devices: Settings > Support > Terms & Policies, then turn off Viewing Information Services.
On LG devices: Settings > General > Privacy & Terms, then uncheck Personalized Advertising. Your TV has been snitching on you, and it’s time to stop it.
4- Prevent the voice assistant from keeping your data
In the Alexa app: More > Alexa Privacy > Manage Your Alexa Data. Delete the history and set how long to retain data.
For Google: go to myaccount.google.com > Data & Privacy, then uncheck Voice & Audio Activity. Every "Hey, Alexa" you’ve said has been saved until you decide otherwise.