A new research paper shows that videoconferencing apps are listening through your microphone even when you appear to be muted. Other participants can’t hear you, but your audio is still being sent to the server.

Muting your audio in a video conference call is a good habit. No one wants to hear the garbage truck outside your window or the washing machine spinning. But we also use mute to let ourselves have a private moment with someone in the room with us, and we might expect mute to mean mute and no audio leaving the computer. But it turns out our private conversations can get a lot further before they’re muted. The good news is there’s a simple solution.

“Users have largely accepted these apps into their personal spaces without much thought about the consent models that govern the use of their private data in meetings,” writes Kassem Fawaz, an assistant professor at the University of Wisconsin, in a research paper. “While access to a device’s video camera is carefully controlled, little has been done to ensure the same level of privacy for access to the microphone.”

The problem is that the microphone is never muted. That is, the microphone is not muted at the input stage. Instead, the audio is sent through your browser to your video conferencing app or the website, and the muting is done at that level.