Britain has launched an initiative to warn security-conscious internet users about a new scam which plays on their knowledge and fear of cybercrime to empty their bank accounts.

Rogue anti-virus, AV scams, fake malware and scareware are all terms to describe the highly organised criminal operation identified this week by Get Safe Online, a joint initiative between the Government, Serious Organised Crime Agency (SOCA) and the private sector.

The scam imitates the style of trusted IT brands to issue phoney alerts and frighten web users into believing their computer has been compromised.

The solution it offers is a ruse to get access to the computer and steal personal financial information.

The scam works this way: A web user gets a pop-up on screen or a cold call from an IT 'help centre' claiming that their computer might be infected by a virus or other malicious software. They are offered a free scan to identify the threats.

If they accept, an authentic looking anti-virus scan appears to take place. In reality, this is no more than an animated sequence.

The scan finds a frightening list of infections and recommends software to fix them.

There is a charge for downloading the full anti-virus package and the user unwittingly hands over their bank account details to a criminal organisation.

To bypass the user's own security software the scam provides details of a call centre to talk the user through the installation process.

The call centre staff effectively direct the unsuspecting user to disable their genuine anti-virus software so the malicious software can run.

Some of the fake call centres have been found to employ hundreds of people.

As part of the initiative, some preventive steps have been suggested like keeping anti-virus and anti-spyware software up to date, making regular back-ups of files containing sensitive information and securing all wireless networks and protecting personal and financial data when online.

If a user sees a pop up or is directed to a site by a cold caller, he is advised to check it out before doing anything.

Some online forums will identify fake products.

Sharon Lemon, Chair of Get Safe Online and SOCA's Deputy Director of Cybercrime, said: "This is big business. In recent cases, we have seen gangs employing 300-400 people to run their operations and using call centre scale set ups to target victims en masse."

"They can also be paying out as much as USD 150,000 a month to individual webmasters who are unwittingly advertising their fake software. This level of investment from criminals indicates that the returns are much heftier than this."

Tony Neate, Managing Director of Get Safe Online, said: "Web users should ignore 'cold calls' from companies offering free virus checks and be very cautious of any on-screen pop ups. Most reputable IT providers do not approach customers in this way without prior notice or a direct request."