Permission for speaker

Why is it that in Qubes Devices I can choose whether or not to give each qubes permission to use the microphone, but I can’t choose whether or not to give the speaker permission?
I think it is dangerous because a speaker can also be a microphone.

In some cases, that’s definitely true. It does also depend on the schematics of the sound card, whether the tracks routing the speaker can be made bidirectional, and the firmware running on the sound card (ie the way the speaker is wired into the card, and whether you can flip a switch somewhere on the circuitboard that will change the speaker output into a microphone input).

This is usually possible with older sound cards, because of the way they were wired. They went for flexibility and versatility, because “security” just wasn’t that much of a concern back then as it is now.

But most modern audio controllers contain one-way diodes in the circuit to the speakers, effectively preventing this from happening.

But failing that, Qubes OS does allow you to specify whether a Qube is allowed audio or not.

If you click on the Volume Control in the top-right corner and select “Audio Mixer…”, you can block sources of audio from getting access to pulseaudio in dom0/sys-audio.

Or, if you like, you can remove the audiovm value of the Qube with:

qvm-prefs $VM_NAME audiovm ‘’