Nearly a quarter (24 percent) of web users have been approached by hoax IT helpdesks, that claim the user's PC is infected with malware, says GetSafeOnline.org.

Research by the UK's internet security initiative revealed the fake helpdesks are the work of cybercriminals, who then try to "sell" web users fake antivirus software, also known as scareware, or offer to fix the PC for a charge.

While the criminals are trying to obtain money, the organization said the ultimate goal is to steal credit card details or install a program that lets the users PC be controlled by the cybercriminal for other illegal activity, such as identity fraud or to launch phishing attacks.

Furthermore, 80 percent of Internet users say they'd never heard of the scam while nearly half (48 percent) have experienced a pop-up window on their PC claiming that their computer has been infected by a virus.

GetSafeOnline.org believes the cybercriminals stand to "make millions while victims are left out-of-pocket, their bank details stolen and their computers seriously compromised."

"While it's encouraging to see that UK web users are today more security-aware, criminals will always try to be ahead of the game and will use increasingly sophisticated methods to take advantage where they can," said Rt Hon Baroness Neville-Jones, Minister of State for Security.

Tony Neate, managing director of GetSafeOnline.org, warned web users to 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," he said.

The research is part of the organization's UK Internet Security: State of the Nation report, which has been compiled as part of Get Safe Online Week that runs from November 15 to 19 and aims to make web users more aware of threats online. Visit GetSafeOnline's website to find out how to spot the tell-tale signs of such scams.

The report also revealed more than a third (34 percent) of web users have been a suffered a virus on their PC, while 22 percent have fallen victim to a phishing scam and 21 percent have had their ID stolen.

See also: How to delete fake antivirus

This story, "Fake Help Desks Trick a Quarter of PC Users" was originally published by PC Advisor (UK) .