Amazon's Alexa Could be Tricked into Spying on Users

Researchers at Checkmarx were able to build an Alexa skill which could be used to spy on users within earshot. Amazon has now closed the loophole.

• By Sydny Shepard
• Apr 26, 2018

Security researchers say they have found a way to make Amazon's Alexa listen in on its users indefinitely, and provide a transcript of everything said in front of the device.

Researchers at cybersecurity firm Checkmarx were able to create an Alexa skill - an applications for the voice-activated assistant - that was able to eavesdrop on users. They created what appeared to be a simple calculator skill for solving math problems but it was actually designed to send transcripts of anything said within earshot of the device back to its creators.

The Alexa service is designed to be fully awake and listening when the user requests the device to list. The active cycle is supposed to be relatively short, with Alexa informing the user when an open session is closed and it is going back to sleep. Researchers decided to examine if the way Alexa listens like this could be exploited.

Once Alexa has performed a task, the code makes a "Should End Session" query, in order to determine if the session remains open or closed after Alexa reads back text, potentially allowing Alexa to stay active for another session. In order to stay active for another session, Alexa sends the user a vocal prompt, informing them that it is still active.

However, researchers found that Alexa's API accepts an empty reprompt code, allowing the vocal prompt to be silent. That means that while Alexa believes it has told the user that the device is still listening, the user is unaware that this is the case.

The blue light on the Echo could give away that the device is still active, but it's possible that users won't notice, or simply won't be looking at the device.

“Echo users need to recognize that 'Alexa Skills' are third-party applications. Just like with any other computing device, users need to be cautious about what applications (or skills) they load and who is providing them. Poorly designed or blatantly malicious applications can lead to degraded user experience as well as privacy or security exposures," security researcher for Tripwire's Vulnerability and Exposure Research Team, Craig Young said. “I would not necessarily call this a security loophole on the part of Amazon. The bottom line here is that for this ‘hack’ to work, a user must load and activate the malicious skill and then ignore the fact that Echo’s blue light remains on.”

Checkmarx disclosed its findings to Amazon, which told the media that it has acted to ensure that skills can no longer be exploited in this way.

"Customer trust is important to us and we take security and privacy seriously. We have put mitigations in place for detecting this type of skill behavior and reject or suppress those skills when we do," a spokesperson said.