A scary new WhatsApp scam has already triggered hundreds of complaints to the police in the UK.
Action Fraud, a UK fraud reporting center, says the new scam revolves around WhatsApp group chats, and uses voice calls to lull people into a false sense of security.
It apparently starts with the scammer calling someone and pretending to be someone from a group chat they're on (presumably someone they don't know in person), and inviting them to an upcoming group call for members of the chat.
They tell their victim to expect a text with a one-time password to let them join the call and ask them to share that code to be admitted.
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This is the key part of the scam since that code is in fact a one-time code generated by WhatsApp when they try to log into the victim's account - registering the account to a new device.
If they succeed in getting access, the scammers reportedly turn on two-factor authentication using their own details, which lets them effectively lock victims out of their own accounts.
From there, things get even worse, since they now have a real and verified user account that they can use to message the victim's friends and family to whatever end they like.
This might mean asking for money to help with a made-up emergency, or it might be even more sophisticated than that - but either way, it's a really bad situation.
Detective Superintendent Gary Miles, head of the National Fraud Intelligence Bureau at the City of London Police, said in a statement: "WhatsApp remains an integral mode of communication for many people across the UK, however, fraudsters still find ways to infiltrate these platforms. Sadly, anyone can become a target for fraud. With more than 630 reports already this year, we are urging users, and in particular, those in big group chats on WhatsApp, to be on their guard and monitor who joins the chats."
It's worth knowing that you should never share login codes or passwords with anyone, to avoid this sort of trap.
It's also handy to be a bit wary of bigger WhatsApp groups - if you know everyone in a chat well, that's one thing, but if there are hundreds of members and plenty of them are strangers to you, you can't necessarily trust them - that might lead to the spread of misinformation, a problem of its own.
WhatsApp itself, meanwhile, had clear advice on the issue: "We recommend that all users set up two-step verification for added security and advise people never to share their six-digit PIN code with others, not even with friends or family."