Thousands of criminals have carried out the UK's biggest-ever fraud - and there are tell-tale signs that you might have been targeted.
The scam saw around 70,000 people contacted over the phone by criminals posing as their bank, the Metropolitan Police said.
These fraudsters stole tens of millions of pounds in what the Met calls the “biggest fraud operation ever run in this country”.
This con is known as "spoofing" as fraudsters use clever software that mimics real bank telephone numbers.
The potential UK victims of the con will be alerted by police this week.
All the UK numbers called by criminals who used the site will be alerted by a Met police text message on Thursday or Friday asking them to contact the force.
How the scam worked
Firstly criminals used cryptocurrency to sign up to a fraud website called iSpoof.
This website let criminals appear as if they were calling from trusted banks, tax offices and other official bodies as they attempted to defraud victims.
At one stage, almost 20 people every minute of the day were being contacted by scammers hiding behind false identities using the site.
They posed as representatives of banks including Barclays, Santander, HSBC, Lloyds, Halifax, First Direct, Natwest, Nationwide and TSB.
The scammers would get their victims' trust.
Sometimes the criminals targeted victims after already knowing some of their banking history - bought from other scammers online.
This made them seem more believable, as they appeared to know information only a real bank would know.
Often the conners then mentioned a made-up transaction which was meant to seem fraudulent, to then worry their victims.
Then the fraudsters would try to steal money in several ways.
These include requesting their victims' passwords, asking them to transfer money to a safe account or getting them to hand over other information that could let fraudsters steal their cash.
How to tell if you've had a real text from the Met Police
The Met is only texting potential scam victims today and tomorrow (November 24 and 25).
If you receive a message outside of this 48-hour window, it could be a scam - so act with caution.
The message will ask you to visit the Met Police website at met.police.uk/elaborate - but the message will not include a direct link.
Instead, you'll need to manually type in the address yourself on a search browser.
The Met is contacting people UK-wide - not just those living in London.
What to do if you think you've been scammed
If you think you've been called by a scammer, never reveal your personal details.
Hang up immediately and search for the contact details online of the place you're supposedly being called from.
Call up the company or bank with the number you found yourself to check if the call was legitimate.
Never call back the number provided by the caller.
You should also call the 159 hotline and report the scam to Action Fraud.
