Study revealed which video call platforms actually mute the microphone

Video calls were essential during the pandemic (Photo: Archive) (zoranm/)

After the pandemic the telecommuting and remote classes became the new normal for millions of people. To achieve this they had to use video call platforms such as Zoom, Skype, Teamsamong others, that give the possibility to turn off the camera and the microphone, however, Is the microphone really off?

One of the facilities of these platforms is to allow the video and audio to be turned off so that external conversations are not filtered or being seen at inconvenient times. The popularity of these apps prompted security experts to check how secure they are.

Kaspersky, cybersecurity company, analyzed whether the microphone mute function in various programs did not actually filter the audio, finding important results that should be taken into account.

Microsoft Teams collaborative work platform (Photo: EP)
Microsoft Teams collaborative work platform (Photo: EP) (MICROSOFT/)

To carry out the investigation, the specialists asked themselves, how is this function really implemented? Is the sound from the microphone sent to the server of the program, even though mute mode is on? And to answer the researchers analyzed the operation of the microphone in a total of ten services, based on calls made through the browser.

What was the results

The cybersecurity company said that in its tests used an open source browser as is the case with Chromium (the basis of many browsers such as Google Chrome and Microsoft Edge).

The goal was for all services to comply with the microphone interaction rules set by the browser engine developers. That is, when the microphone mute button is activated in the web interface, the service should not pick up any sound. Native desktop apps have more permissions.

The result was, as expected, that each program has a different behavior. The results for each of the video call platforms were as follows:

Small toy figures are seen in front of the displayed Zoom logo (Photo: REUTERS/Dado Ruvic)
Small toy figures are seen in front of the displayed Zoom logo (Photo: REUTERS/Dado Ruvic) (Dado Ruvic/)


Is trustworthy: Microphone mute mode does not listen to what is happening around you. In addition, it regularly requests information that allows it to determine the noise level near the microphone. As soon as it detects a noise or a voice, it remembers, as always, that the audio should be activated.

Microsoft Teams

Things are a bit more complicated. Microsoft Teams does not use the standard system interface for microphone interaction, instead communicates directly with Windows. For this reason, the researchers could not find out in detail how you manage silent mode during a call.


It constantly processes the sound from the microphone during the call, regardless of the state (on or off) of the audio within the application. The researchers discovered that Webex does not spy as such, since, in silent mode, sound is not transmitted. But it does send metadata like the volume level of the signal.

Video calls through Cisco Webex (Photo: EP)
Video calls through Cisco Webex (Photo: EP) (CISCO/)

It seems somewhat worrying. However, they were able to guess a number of basic parameters of what was happening in the user’s environment. For example, it was possible to determine if the user, being connected to a work call, had turned off the microphone and the camera and was vacuuming, cooking or there was a dog barking close.

Until they were able to tell if there were other people in the room (for example, determining that the call came from a public place). The specialists used an algorithm similar to that of Shazam and other music recognition applications. For each “noise sample,” a set of patterns was created and compared to data captured from the Cisco Webex client.

It should be noted that the real danger is not these tools, but the malware which can spy on the victims and send the audio recordings of those conversations. In this case, you need not only a security solution that deals with unwanted programs, but also a means to control who accesses the microphone and when.


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