The right to
Where are those files sent and how?
As you speak those magic words, the files are recorded but they do need an internet connection to be sent to the real brains behind the technology. As the files are uploaded over cloud, the server generates a response and that’s how it goes.
Why are they doing it?
There's a base on how voice assistants function. Listening to what you say before a wake word is fundamental to the whole idea of those words. Audio pre-recording helps systems handle requests immediately. Without a livened ear for that
How to stop them
Press the mute button and that’ll disable your device from listening anything. There’s no other way for now, but soon we’ll see something like an incognito mode for these home assistants.
For a permanent stopping of the snoop-tales (for Google Home), try disabling your audio or video recording from here. But let me warn you, it’ll make your device a standing rock (doing nothing) for some time.
For Alexa, just press the mute button or bare the pain for a while.