Millions tricked by 'scareware'

Online criminals are making millions of pounds by convincing computer users to download fake anti-virus software, internet security experts claim.

Symantec says more than 40 million people have fallen victim to the "scareware" scam in the past 12 months.

The download is usually harmful and criminals can sometimes use it to get the victim's credit card details.

The firm has identified 250 versions of scareware, and criminals are thought to earn more than £750,000 each a year.

Franchised out

Scareware sellers use pop-up adverts deliberately designed to look legitimate, for example, using the same typefaces as Microsoft and other well-known software providers.

They appear, often when the user is switching between websites, and falsely warn that a computer's security has been compromised.

If the user then clicks on the message they are directed towards another site where they can download the fake anti-virus software they supposedly need to clean up their computer - for a fee of up to £60.