If you receive a cold call at home from a stranger claiming to fix your PC viruses, then whatever you do, don't give them the time of day.
The advice seems obvious to seasoned computer users, although new reports claim that up to a quarter of British internet users have already received such calls and many have been fooled by them.
The criminal cold-callers offer to fix any virus problems the user may have with their PC, but then installs spyware on their computers in order to steal valuable personal info.
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PC safety campaigners group Get Safe Online has said that the cyber-crime gangs employ up to 400 people in secretive call centres to target as many unsuspecting Brits as they can.
Get Safe Online is an organisation backed by the British government, police forces and a number of major companies with a stake in UK internet security.
"Rather than exploiting our ignorance... they are actively using our knowledge and fear of online threats to their advantage," criminologist Dr Emily Finch from the University of Surrey says of the latest wave of attacks from online cyber-crims.
To trick unsuspecting and inexperienced PC users, gangs use spyware products that look very similar to professional (and well recognised) anti-virus brands.
The gangs also use call centres in eastern Europe or Asia to cold-call Brits to gain access to identity info which allows them to quickly perform credit card scams and other online rip-offs.
Sharon Lemon, deputy director of the UK's Serious and Organised Crime Agency (Soca) told the BBC: "In recent cases, we have seen gangs employing 300 to 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 $150,000 (£92,000) 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."
Baroness Neville-Jones, minister of state for security, says of the latest scams: "Given that our latest research indicates 80% of UK internet users have never heard of these 'IT helpdesk' scams, yet almost a quarter have been approached by them, it is vital that we make people aware of this threat."
You can see the latest Get Safe Online annual report online.
Via BBC News