Online safety group Get Safe Online has warned the public about the rising number of fake anti-virus scamsters cold-calling Brits, offering to fix their computers but installing information stealing spyware instead.
The group, which is backed by the government, police officials and the private sector, said to the BBC that more than a quarter of people interviewed had received such calls from scammers.
Get Safe Online reports that the gangs are operating out of secret call centres within the UK, Eastern Europe and Asia and every such call centre employs around 400 people.
The group also warned people to be wary of suspicious looking anti-virus pop-ups that offer to 'check' and 'clean' the system.
The aim of the gangs is to extract personal information or install malicious content, with sole purpose of stealing money.
Tony Neate, head of Get Safe Online, told the BBC that one of the gangs operating out of eastern Europe managed to rake in £4.5 million last year.
Commenting on the issue Neate said: “This is big business, and it's preying on people's fears of the internet. The internet is a great place but when somebody phones you up and tells you you have a virus on your machine, you will start to panic.”