U.K. police struggle to contact people whose passwords and credit card details have been stolen.
The Metropolitan Police said on Tuesday that a computer seized in the U.S. had been found to contain personal information from around 2,300 PCs based in Britain. This included e-mail addresses, passwords, credit card numbers and details of online transactions.
According to the Metropolitan Police Computer Crime Unit, the data was stolen via a piece of malicious software that was secretly installed on the victims' machines.
"The information has been harvested from the computers by a type of malicious code known as a 'backdoor,'" a detective from the Computer Crime Unit said in a statement. "It is too early to establish at this early stage how the computers have been infected. However, there are thousands of computer users worldwide who have had their computers compromised and data stolen."
The Metropolitan Police would not say whether the information has been used to defraud victims. The 2,300 people whose data was found are being contacted by the police via e-mail. However, it appears that the warnings are often being ignored.
"We're appealing for anyone who's had an e-mail from the Met officers who work in the Computer Crime Unit to get in touch. There's a security measure that people have to go through when they ring, but people are ignoring the e-mails because they think they're a hoax," a Metropolitan Police representative said.
The Metropolitan Police also declined to reveal the circumstances behind the seizure of the U.S. computer, as the investigation is ongoing. They also declined to say which Internet service providers and banks are being alerted.
Graeme Wearden and Tom Espiner reported for ZDNet UK from London.