Crooks are targeting Snapchat and Instagram users and blackmailing them into handing over cash.
The scammers have been tricking people into telling them their two factor authentication (or 2FA) code, then using it to access their social media accounts.
The criminals have then been threatening to share private photos of others, unless money is handed over.
Never hand over 2FA codes
The 2FA is a security measure that kicks in when a social media account is logged into from a device that is not recognised. It texts the user a unique code that they must then enter along with their password in order to access the account.
Both Snapchat and Instagram use this feature in an attempt to stop accounts being fraudulently accessed.
But the Met Police, along with the anti-fraud policing branch Action Fraud, have issued a fresh warning that scammers are cracking the system. So far, Action Fraud has received more than 70 reports of the scam.
Police are now warning people to stay alert for emails and text messages asking for the codes sent by 2FA.
A statement said, "The team @actionfrauduk are seeing an increase in the number of accounts targeted.
"Don't respond to messages that ask for your login details or two-factor authentication codes. These can be used to compromise your account."
Users are advised to report any suspicious correspondence and to flag any spam messages.
How to spot a fake email or message
Your bank or the retailer will always address a customer by name. They will never ask a customer for their PIN, password or full memorable information.
The bank would never ask a customer to click on a link in an email or text message that takes you to a page which asks you for your username, password or any other information. They would never ask a customer to email or text them PINs, card details or passwords
Customers should not click on any links in emails if they have concerns. Customers are encouraged to call their bank if they are concerned about an email they have received.
This article originally appeared on our sister site The Yorkshire Post.