Cloned voices: hang up, call back, family password

A few years ago, imitating someone's voice took a talented impressionist. Today, tools available to anyone can reproduce a voice from a short recording. Over the phone, where the sound is already mediocre, a few seconds of material can be enough to fool a worried ear.

How it's possible

A speech synthesis model has learned, from huge amounts of recordings, how a human voice works in general. All it has left to do is capture what makes your voice unique: the tone, the rhythm, the accent. For that, a clip is enough: a video posted on social media, a voice message, a few sentences recorded during a call where a stranger got you talking. The more material, the closer the imitation; but over the phone, in a panic, an imperfect imitation often gets through.

The typical scenario

A call from an unknown number. Your daughter's voice, in tears: "Mum, I've had an accident, I need money, don't tell Dad." Then, often, someone else takes over: a so-called lawyer, a police officer, a mechanic, who gives the payment instructions. The call is short, choppy, urgent. Everything is designed so you don't have time to think.

Three simple defences

• Hang up and call back: hang up, then call the person back yourself on the number you already have in your contacts. Not the one that just called you, not the one you're given. If they don't answer, call someone close to them. A real emergency can survive two minutes of checking.
• The family password: agree with your loved ones on a secret word or short phrase, known only to you, never written online. If you get a worrying call, ask for it. A cloned voice doesn't know it. Choose it face to face, as a family, not by message.
• The trick question: if you have no password, ask a question only your real loved one can answer, and whose answer is nowhere on social media: "What did we eat at Grandma's last Sunday?" Avoid questions whose answer can be guessed or found online (birthday, place of birth, the name of the dog in your photos).

Limiting the material out there

You don't have to vanish from the internet. But bear in mind that your public videos, your voice messages and even your voicemail greeting are usable audio. On a public account, prefer videos without your voice, or keep them for a small circle. And if a stranger calls and tries to keep you talking for no clear reason, cut it short.