[thudrs]

It is in the hardware. You can take one apart and see for yourself. These devices will not activate unless they at least think they hear the hotword. Once activated though, nothing is stopping them from staying on. Although Im sure you can just watch their internet traffic to prove if its listening in the moment.

[mercer]

You'd have to do that 24/7 though, if I understand correctly, because these devices can be updated at will.