You’re chatting with a coworker about replacing the office coffee maker, and by lunchtime your phone is showing you ads for espresso machines. It’s enough to make anyone look at their phone with a little suspicion. The explanation the research supports is less dramatic than eavesdropping, but it still matters for businesses, because the data trails that shape your ads also come from the company phones and laptops your team carries every day.
What Researchers Found About Microphones
The popular theory is that apps secretly switch on your microphone, listen for keywords, and pass them along to advertisers. In 2018, researchers at Northeastern University tested that idea by running automated tests on more than 17,000 popular Android apps, including Facebook and thousands of apps that send data to it.
In that testing, they found no evidence of apps secretly recording audio and sending it out. The researchers were careful not to call this proof that it never happens. The study is also several years old and covered only Android, so it is best read as one strong data point rather than the final word on today’s apps. They did uncover a different concern, which was that some apps were sending screenshots and screen recordings of user activity to outside companies without telling users. You can read Northeastern’s summary of the study or the full research paper.
The “Active Listening” Claims
In December 2023, 404 Media reported on a marketing firm’s “Active Listening” pages, which claimed the firm could target ads using conversations picked up by phones, smart TVs, and other devices. In August 2024, 404 Media followed up by publishing the firm’s pitch deck for the service, and after that second report, Google removed the firm from its advertising Partners Program.
It was never shown that the service actually worked as described, so these remain claims rather than a confirmed case of phones listening for ads. It’s also worth knowing that current iPhones and Android phones display an indicator whenever the microphone is in use.
Where the Data Actually Comes From: Location
Many apps collect location data, and research shows it can reveal more than where you are. A paper from NYU’s Stern School of Business on location-based ad targeting notes that when two phones regularly appear in the same place, it’s a strong sign their owners know each other, and it explores how advertisers could use that connection.
A study published in the Journal of Marketing, “Predicting Mobile Advertising Response Using Consumer Co-Location Networks,” looked at this directly. Researchers followed 217 people for three months as they received mobile coupons, with their location recorded every hour. People who had been in the same place at the same time tended to respond to coupons in the same product categories. Within that study, adding location data made the researchers’ predictions of which coupons people were most likely to redeem 19% more accurate. The participants didn’t need to know each other, since people with similar tastes tend to visit the same places.
How Someone Else’s Search Could Become Your Ad
Location isn’t the only possible link between you and the people around you. Devices on the same Wi-Fi network often share one internet address, which ad systems can use to group devices into a household or workplace.
A patent on file with the U.S. Patent and Trademark Office for “connected household” ad targeting also describes linking households so that one household’s traits influence the ads shown to another, including households a person has visited. A patent shows that a technique has been described, not that a particular platform uses it, so think of this as one possible mechanism rather than the explanation for any specific ad.
Two simpler factors can also play a role. Conversations often happen because something is already on someone’s mind, whether from a search, a website, or a store visit, and that earlier activity is visible to ad systems in a way a conversation is not. There’s also a well-known quirk of attention called the frequency illusion, where you notice the one ad that matches your conversation and overlook the dozens that don’t.
Why This Matters for Business Devices
For a business, these settings are more than a personal preference. Location history on a company phone can show which clients your team visits, how often they go, and where people travel for work, and the apps on that phone determine who has access to that information.
A permissions review is worth assigning to whoever manages your devices, whether that’s the owner, an office manager, or an IT provider. It should cover company-owned phones, tablets, and laptops, along with personal phones that people use for work email or business apps. The goal isn’t to lock everything down, but to make sure each app has only the access it actually needs.
Turning Down the Volume
There’s no single switch that makes anyone invisible to advertisers, because targeting draws on many sources at once. You can, however, reduce how much data you share, and most of these steps take only a few minutes.
- Review location permissions. In your phone’s settings, change apps from “Always” to “While Using” or “Never,” and turn off precise location for apps that don’t need it. A weather app needs your city, not your front door.
- Limit ad tracking. On iPhone, go to Settings, then Privacy & Security, then Tracking, and turn off the option that lets apps ask to track you. On Android, look for the Ads section under Privacy settings and delete your advertising ID (the exact location varies by device).
- Check microphone and camera access. Secret listening isn’t supported by the evidence, but a flashlight app still has no reason to use your microphone, so remove permissions that don’t make sense.
- Review your ad profiles. Google’s My Ad Center and Meta’s Ad Preferences let you see the interests these platforms have assigned to you, turn off personalized ads, and manage information shared with them by other businesses. Reading the list of interests can be entertaining on its own.
For those who want to go further, companies called data brokers buy and sell personal information, including location data. California residents can use DROP, the state’s Delete Request and Opt-out Platform, which launched in 2026 and sends one deletion request to every data broker registered in California. Deletion isn’t absolute, since brokers can only remove records they can match to the details provided, and some data is exempt, such as public records and information a company collected directly from you. In most other states, opting out still means contacting brokers one at a time.
The Bottom Line
The research to date hasn’t found evidence that phones eavesdrop on conversations to serve ads, but location data, shared networks, and everyday browsing give advertisers plenty to work with. If you’d like a simple place to start, pick one company phone this week, walk through the four steps above, and then add the same review to your checklist for setting up new devices. Just keep expectations realistic, because opting out won’t mean fewer ads, only ads that know a little less about the office coffee maker.
Posted by Nathan R on October 19, 2026