A family in the United States has vowed to never use Amazon's virtual assistant Alexa again after the device recorded a private conversation in their home and sent it to a random contact.

Danielle (surname withheld) told KIRO-TV she received a call from an employee of her husband who urged them to unplug their Echo devices, which use the Alexa software.

She said the employee then revealed he had been sent an audio file of what was going on in their Portland home.

The employee lived in Seattle — 282 kilometres away.

"I felt invaded, like total privacy invasion," Danielle said.

"I'm never plugging that device in again — I can't trust it."

Danielle said when she contacted Amazon, an Alexa engineer confirmed the conversation had been recorded and sent it to a contact without their consent.

She said the engineer told her Alexa had "guessed" what they were saying.

"He apologised like 15 times in a matter of 30 minutes and said, 'We really appreciate you bringing this to our attention, this is something we need to fix'," she said.

Amazon has described the event as an "extremely rare occurrence".

In a statement provided to several media outlets, an Amazon spokesman explained why they believe the incident occurred.

"Echo woke up due to a word in background conversation sounding like 'Alexa'. Then, the subsequent conversation was heard as a 'send message' request. At which point, Alexa said out loud 'To whom?' At which point, the background conversation was interpreted as a name in the customers contact list. Alexa then asked out loud, '[contact name], right?' Alexa then interpreted background conversation as 'right'. As unlikely as this string of events is, we are evaluating options to make this case even less likely."

Like Apple's Siri, Alexa is a digital assistant built into several Amazon devices.

The program activates by saying the word "Alexa", then a command, like "play music".

Alexa caught randomly laughing at people

Recording and sharing a private conversation without consent is the second incident this year that has raised concerns about Amazon's virtual assistant.

Several people reported strange occurrences of Alexa laughing at them for no reason in February and March.

Amazon said Alexa could mistakenly hear the phrase 'Alexa, laugh' and that it would change the phrase to 'Alexa, can you laugh?' to reduce the number of false positives.