Hackers can trick voice services such as Alexa and Siri with 'silent' commands

Researchers from China's Zheijiang University have discovered a new way to access the AI assistants on your smartphone, tablet and other devices without your knowledge. 

By using ultrasonic frequencies that are too high for humans to hear, the researchers were able to send commands to Siri, Alexa and other voice assistants to access a wide range of functions on a number of popular consumer devices.    

The technique they employed is known as DolphinAttack and the entire process involved translating human voice commands into ultrasonic frequencies over 20,000 hz and then playing them back through a smartphone equipped with an amplifier and an ultrasonic transducer.  Surprising all of the equipment needed to perform this hack costs less than $3 in parts. 

DolphinAttacks are particularly unsettling because they can be used to access almost any device with a voice assistant such as Amazon's popular Echo devices, Apple's iPhone and iPad, Android smartphones and tablets and even the navigation system of an Audi Q3.  Though the commands sent to the devices were inaudible to the human ear, they can still be correctly interpreted by the speech recognition systems on these devices. 

While this attack method could potentially pose a serious threat, for now its range is limited to five or six feet and device makers could reprogram their products to ignore commands at 20 Khz or other frequencies out of the range of human communication. 

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