http://www.techradar.com/news/amazons-alexa-can-now-recognize-individual-voices-and-users >Amazon just made it a little harder for someone else to hijack your Echo – the Alexa voice assistant can now recognize individual voices and personalize its response, so you and the rest of your family can use your smart speakers without any overlap. >You can set up voice recognition on an Amazon Echo, Echo Dot, or Echo Show by reading aloud 10 phrases to create a voice profile (there's a tutorial video here). Alexa will then be able to identify you across any Echo device and 'most' third-party devices with Alexa attached, Amazon says.