Ask HN: Are computers listening/recording when off?

Edward Snowden in an interview with MSNBC on Sept. 17th 2019 says computers are listening and recording video even when off. Ed also says he desolders his mic and camera (and plugs in a mic when necessary).

If this really is happening, would engineers working on Android & Apple phones be aware of this? And if they are aware, are there posts stating this on HN?