In the UK and elsewhere, scammers - usually calling from the Asian sub-continent - continue to catch out the unwary, hitting them for money, stealing their credit-card details and infecting their PCs into the bargain .

That's not surprising, though, when a huge number of people simply do not understand that it is impossible for anyone who calls them up to know whether or not their computers are infected.

Below is an edited extract from an email I sent this week to a client whom (I later learned) just pulled back from the brink and refused to allow a scammer to take remote control of her computer.

Other clients (all men, oddly) have been less fortunate and have ended up with infected PCs; compromised credit cards, ID and internet security; and substantial bills to put right the damage caused by these fraudsters, plus a whole lot of inconvenience.

I phoned your home as soon as I got your email and left a message asking you to call me BEFORE you use your computer!

That's because, sadly, the 'company' that called you up is bogus - this is a long-running scam that has been going for over two years and is widely reported on traditional media and also on highly-respected sites, including the BBC and The Guardian.

Here is a forum thread on moneysavingexpert that also makes interesting reading and below are some links on techie sites about this type of fraud:

http://www.pcpro.co.uk/news/security/359233/the-unstoppable-tech-support-scam

http://www.theregister.co.uk/2009/04/10/supportonclick_scareware_scam/

http://www.digitaltoast.co.uk/supportonclick-systemrecure-scam

http://forums.whirlpool.net.au/archive/1200200

There are call-centres full of people making these fraudulent phone calls and they are raking in huge amounts of money - from the infections that they put on PCs (some of which can compromise your online shopping and banking) and from the folks who get conned and cough up money, divulging their credit-card details [to fix problems that the baddies themselves have introduced!].

If, as appears to be the case, you allowed them access to your PC, please switch if off without using it any further and bring it to me so I can disinfect it and undo any other damage they may have caused.

But whatever you do, PLEASE call me asap and immediately stop using the PC if you did let the scammers connect to it.

The bottom-line here, of course, is that you shouldn't trust cold-callers on the phone when, almost certainly, you wouldn't trust them at your front door (and, hopefully, not in email, either) .

Trouble is, too many supposedly reputable companies, including banks, do the most stupid things. My own bank cold-calls me and demands security details (yes, it really does).

And I was far from impressed when it recently added a 'remember' me option to its ebanking site!

So, it's hardly surprising that people don't always have their guard up and, thus, can easily get ensnared by smooth-talking fraudsters. Most know little about computers because, understandably in my view, they regard them as tools, not things to worship as some of us techies do.