A gang of online bank robbers that has taken over the accounts of at least ten people and stolen hundreds of thousands of pounds is being hunted by an anti-fraud unit.

The gang hacked into private bank accounts and used private details to order new debit and credit cards which it then used to buy expensive jewellery, electronic goods and euros.

The gang managed to get enough information about one victim to have £60,000 transferred from his mortgage reserve account to his current account, which it then spent.

Barclays Bank managed to intercept much of the fraud and is believed to have stopped at least £500,000 being stolen from clients. But officers from the Dedicated Cheque and Plastic Crime Unit say that there may be many more victims.

Detective Constable Keith Harrington said that the gang’s favourite method was a process known as “account take over”, in which the thieves got enough private information to convince a bank that they were the customer and then ordered a new card and PIN.

“The whole operation from start to finish takes a few days and usually by the time anyone notices the money has gone the gang will have bought the goods and sold them on,” DC Harrington said.

“There are a number of victims. When we first came across it we thought it was unusual but we have found it is happening all over the country.”

One victim, Bob Whitaker, came home from a trip to Thailand with his wife to find that the gang had used a debit card in his name to buy £60,000 of jewellery from a store in Barcelona.

It is believed that by using a technique known as “social engineering” – where a gang member rings up a bank’s staff and feigns memory loss – the thieves were able to find out from Barclays Bank where Mr Whitaker held his mortgage.

They then rang the mortgage company and gave enough information to convince the staff to transfer £60,000 from his mortgage reserve account into the current account of which they had taken control.

After ordering a new debit card and PIN from Barclays the gang is thought to have paid a middle-aged, white drug user to pose as Mr Whitaker and collect his mail from his local postal sorting office using fake indentification.

They were then able to open the letters that contained the new card and PIN and posted everything else through Mr Whitaker’s door to prevent him becoming suspicious.

Within days of beginning the operation the gang had either gone to Barcelona and bought the jewellery or sold the card to a gang in Spain which made the purchases.

Mr Whitaker, 57, an IT director of a manufacturing company, who has been reimbursed by Barclays, said that when he telephoned the bank and found out that there was £60,000 in his account his first thought was that the money might have come from a money-laundering scam. “My second thought was to take [the money] out,” he said.

“It seems [the gang] told Barclays that ‘I’ needed a new debit card as the current one was damaged and a reminder of the PIN and then all they had to provide as identification to the Post Office was a Tesco Clubcard and a fake utility bill.

“Somehow or other they managed to convince my mortgage company to transfer the £60,000 and then used the new card to spend it. This has all been rather disconcerting, especially finding out how easy it is for people to pretend to be me and how easy it was for them to get to my post. It is not as though I am lax with my internet security, I am very careful and work in IT so have all the spyware and never respond to stupid emails so I honestly don’t know how they got my details.”

Larry Bridwell, from AVG, a global internet security company, said: “It may be that the criminals have been monitoring their victims and their habits and then used that information to use social engineering. People have to remember that there is no such thing as privacy in the online world.”

Barclays said that it was inappropriate for them to comment during an investigation.

A Royal Mail spokesman said: “Security is a top priority for Royal Mail and we constantly review it to ensure we do all we can to combat criminals who target the mail.”

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