蜜芽传媒

Virtual assistants activated by voice commands are on the rise. The best known are probably Apple's Siri and Amazon's Alexa, which has recently popped up in a range of devices including fridges, cars and robots.

But, as Chris Vallance found out, they could be vulnerable to attacks using hidden sounds.

(Photo: A product using Alexa is demonstrated on stage at the Consumer Electronics Show in Las Vegas. Credit: Getty Images)