Scam callers targeted people in the Durham area on Wednesday claiming that their bank accounts had been compromised.
The fraudsters, who claimed to be police officers, told the victims that in order to secure their accounts they needed to withdraw £5,000.
They also claimed that they needed to buy something of high value to hand to a courier who was working with the police to safeguard their accounts.
Detective Constable Sarah Douglas, from Durham CID, said: “Fraudsters who take part in this type of criminal activity will often pick out the most vulnerable members of society, so we are urging people to be vigilant and warn their friends and family, especially in the run up to Christmas.
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“They often use well-rehearsed stories to gain their victims trust and can often seem very genuine.
“We want to remind people that genuine police or bank staff would never ask you to withdraw or transfer cash from your account.
“Thankfully in this case, the victims did not hand over any money or assets over to the conmen but this could very easily have had a different outcome.”
Police have issued the following advice on how to avoid falling victim to scammers:
• The police will never ask you to become part of an undercover investigation or for you to withdraw cash and hand it to them for safe-keeping.
• Be wary of any calls, texts or emails purporting to be from the police asking for your personal or financial details, or for you to transfer money.
• If you are approached, or feel something is suspicious, hang up the phone and don’t reply. Then report it to Action Fraud and your bank on their advertised number.
• The telephone is a key route into the homes and lives of fraud victims. If you receive an unsolicited call, then hang up and take five minutes to verify the call via trusted means.
• If you have suspicions or would like to report fraudulent activity, contact police on 101, or call Action Fraud on 0300 123 2040.