Recent security research shows that soundcards support surreptitiously switching line-out jacks into line-in by modifying the software stack. The way modern speakers and headphones are designed makes them readily usable as microphones. The Intel High Definition (HD) Audio standards which all modern consumer soundcards are based mandates this stupidity. https://arxiv.org/ftp/arxiv/papers/1611/1611.07350.pdf Does anyone know if QEMU's emulated sound devices follow this standard? If yes then a malicious guest that can modify the virt sound hardware can turn PC speakers into surveillance devices even if the microphone is disabled on the host. The only solution is completely denying untrusted VMs access to a virtual sound device. /CC'd the respective researchers for input on this too.