Attackers can force Amazon Echos to hack themselves with self-issued commands

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Aug 17, 2014
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Academic researchers have devised a new working exploit that commandeers Amazon Echo smart speakers and forces them to unlock doors, make phone calls and unauthorized purchases, and control furnaces, microwave ovens, and other smart appliances.

The attack works by using the device’s speaker to issue voice commands. As long as the speech contains the device wake word (usually “Alexa” or “Echo”) followed by a permissible command, the Echo will carry it out, researchers from Royal Holloway University in London and Italy’s University of Catania found. Even when devices require verbal confirmation before executing sensitive commands, it’s trivial to bypass the measure by adding the word “yes” about six seconds after issuing the command. Attackers can also exploit what the researchers call the "FVV," or full voice vulnerability, which allows Echos to make self-issued commands without temporarily reducing the device volume.

Because the hack uses Alexa functionality to force devices to make self-issued commands, the researchers have dubbed it "AvA," short for Alexa vs. Alexa. It requires only a few seconds of proximity to a vulnerable device while it’s turned on so an attacker can utter a voice command instructing it to pair with an attacker’s Bluetooth-enabled device. As long as the device remains within radio range of the Echo, the attacker will be able to issue commands.

The attack "is the first to exploit the vulnerability of self-issuing arbitrary commands on Echo devices, allowing an attacker to control them for a prolonged amount of time," the researchers wrote in a paper published two weeks ago. “With this work, we remove the necessity of having an external speaker near the target device, increasing the overall likelihood of the attack.”
As noted earlier, Amazon has fixed several of the weaknesses, including one that used Alexa skills to self-wake devices, that made it possible to easily use radio stations to deliver self-issued commands. In a statement, company officials wrote:
At Amazon, privacy and security are foundational to how we design and deliver every device, feature, and experience. We appreciate the work of independent security researchers who help bring potential issues to our attention and are committed to working with them to secure our devices. We fixed the remote self-wake issue with Alexa Skills caused by extended periods of silence resulting from break tags as demonstrated by the researchers. We also have systems in place to continually monitor live skills for potentially malicious behavior, including silent re-prompts. Any offending skills we identify are blocked during certification or quickly deactivated, and we are constantly improving these mechanisms to further protect our customers.
 
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