https://phys.org/news/2018-06-amazon-alexa-devices-hotels-privacy.html

But as long as there's a way to turn off the devices, there's no need to worry, said Chris Clifton, a professor of computer science at Purdue University, who studies data privacy.

"There is a mute button on the device which, when pressed, makes Alexa unable to hear anything," he said. "You could also just unplug it."