The mute button does not stop the video calling software from listening to the microphone. Researchers from two American universities discovered this in Mute buttons analysis In programs such as Skype, Teams, Zoom and Slack. Cisco Webex was also investigated, and found to be sending audio data to its servers for telemetry even with the microphone muted.

We’ve tested it ourselves, and Skype’s mute button doesn’t actually provide driver-level mic muting. This can be useful if the microphone is used in several programs at the same time, but this allows the program to continue listening. According to the researchers, most of the tested apps do not use this option.

The exception is Cisco’s Webex, a video conferencing software aimed at the business market. Webex was fetching data from the microphone every minute, even if the audio was muted. This included audio-derived data, such as the volume of background sounds. So there are no audio portions recorded, but according to the research, there is enough information to be able to identify the activities that were performed in the background.

Cisco responded to the findings of the investigation. The company has a news site Let the record know They modified their programmes; No more microphone data will now be sent to servers, other than information used for Webex’s mute notification feature.

The 21-page investigation into the mute buttons Available online in pdf format On the Wisconsin Privacy and Security Group website.

sources:
Study “Are You Really Silent?” (PDF)† record