The Amazon Echo has been in the news recently, thanks to a murder case in Arkansas in which a man named Victor Collins was murdered at the residence of James Bates. Mr. Bates owned an Echo device, and the police seized the Echo after obtaining a warrant to search the home. The police then issued a warrant on Amazon requesting information that may have been uploaded by the device to their servers. The warrant claims that because the Echo is always listening for its wake command ('Alexa') it may record statements made in its vicinity even if the wake command is not given. Amazon contests this and says that device will not record any audio, unless someone says the magic word, 'Alexa'. It has refused to comply with the warrant. In the TV news report I listened to today, a reporter claimed that the hardware itself only keeps 90 seconds of audio recordings, but I have not been able to confirm this online.
Regardless of whether or not the Echo records conversations that are not directed to it, it certainly does a remarkable job of recording anything you do ask it, and how it responds, and saving that information in the Cloud.
Your Amazon Echo history can be accessed using the Alexa app on your smartphone. As you can see it has a record of each request you made to going back in time months and months. [Presumably the data is kept in the cloud indefinitely unless the user takes action to remove it - I'm unclear on this point. However I can report that on my home device it kept audio of requests going back at least 6 months.]
The requests are not only logged, but a recording of your statement to the device is made and can easily be played back on your smartphone.
A note on how the Echo responded is also kept. The recordings can be deleted one by one, or you can choose to purge the voice recordings at this site:
Click on the 'Your Devices' tab, choose your Echo, and then find the link to the left which reads, 'Manage voice recordings'. You should see this message:
Intriguingly, damning evidence may have been obtained in the Collins murder case from the home's water meter. It shows that 140 gallons of water were used in the home between 1 am and 3 am on the night of the homicide. Police speculate that the water was used to wash down the patio of the home after Mr. Collins was murdered in the backyard hot tub.