As a matter of principle, it is possible to eavesdrop on rooms using microphones in end devices. A distinction is made between two variants here:

The first involves end devices that can be prompted to activate their built-in microphones from the public network or via LAN if corresponding functions are implemented. A well-known example of this is the “baby monitor” function available in some phones or answering machines.

The second variant involves misuse of the “voice calling” feature in combination with the “handsfree” option. This combination can cause the target system to operate like an intercom system under certain circumstances, which makes it possible to eavesdrop on a room.