Some computer science academics at Northeastern University had heard enough people talking about this technological myth that they decided to do a rigorous study to tackle it. For the last year, Elleen Pan, Jingjing Ren, Martina Lindorfer, Christo Wilson, and David Choffnes ran an experiment involving more than 17,000 of the most popular apps on Android to find out whether any of them were secretly using the phone’s mic to capture audio. The apps included those belonging to Facebook, as well as over 8,000 apps that send information to Facebook.
Sorry, conspiracy theorists: They found no evidence of an app unexpectedly activating the microphone or sending audio out when not prompted to do so. Like good scientists, they refuse to say that their study definitively proves that your phone isn’t secretly listening to you, but they didn’t find a single instance of it happening. Instead, they discovered a different disturbing practice: apps recording a phone’s screen and sending that information out to third parties.
Of the 17,260 apps the researchers looked at, over 9,000 had permission to access the camera and microphone and thus the potential to overhear the phone’s owner talking about their need for cat litter or about how much they love a certain brand of gelato. Using 10 Android phones, the researchers used an automated program to interact with each of those apps and then analyzed the traffic generated. (A limitation of the study is that the automated phone users couldn’t do things humans could, like creating usernames and passwords to sign into an account on an app.) They were looking specifically for any media files that were sent, particularly when they were sent to an unexpected party.
The strange practice they started to see was that screenshots and video recordings of what people were doing in apps were being sent to third party domains. For example, when one of the phones used an app from GoPuff, a delivery start-up for people who have sudden cravings for junk food, the interaction with the app was recorded and sent to a domain affiliated with Appsee, a mobile analytics company. The video included a screen where you could enter personal information—in this case, their zip code.
In other words, until smartphone makers notify you when your screen is being recorded or give you the power to turn that ability off, you have a new thing to be paranoid about. The researchers will be presenting their work at the Privacy Enhancing Technology Symposium Conference in Barcelona next month. (While in Spain, they might want to check out the country’s most popular soccer app, which has given itself permission to access users’ smartphone mics to listen for illegal broadcasts of games in bars.)
The researchers weren’t comfortable saying for sure that your phone isn’t secretly listening to you in part because there are some scenarios not covered by their study. Their phones were being operated by an automated program, not by actual humans, so they might not have triggered apps the same way a flesh-and-blood user would. And the phones were in a controlled environment, not wandering the world in a way that might trigger them: For the first few months of the study the phones were near students in a lab at Northeastern University and thus surrounded by ambient conversation, but the phones made so much noise, as apps were constantly being played with on them, that they were eventually moved into a closet. (If the researchers did the experiment again, they would play a podcast on a loop in the closet next to the phones.) It’s also possible that the researchers could have missed audio recordings of conversations if the app transcribed the conversation to text on the phone before sending it out. So the myth can’t be entirely killed yet.