The National Crime Agency is warning computer users they have two weeks to protect against a “powerful computer attack”.
It comes as US officials held a press conference accusing a Russian hacker of masterminding the scam and raking in £60m.
Two pieces of malware software known as GOZeuS and CryptoLocker are at the centre of the alert.
People are being warned to make sure their security software and operating system are both up to date, and to run scans to check for any problems.
Important files should also be backed up, said the UK’s National Crime Agency (NCA).
The malware typically infects a computer via attachments or links in emails.
If a user clicks on one of them, the malware silently monitors activity and tries to capture any private information, such as banking details.
“(The links or attachments) may look like they have been sent by genuine contacts and may purport to carry invoices, voicemail messages, or any file made to look innocuous,” the NCA warned.
“These emails are generated by other victims’ computers, who do not realise they are infected, and are used to send mass emails creating more victims.”
The agency said GOZeuS (also known as P2PZeuS) was responsible for hundreds of millions of pounds of fraud globally… see more