Mandy McClenaghan was contacted by a man claiming to be from computer giant Microsoft about a possible computer problem.

However, working in internet and computer security, the 48 year old knew better and questioned the caller on how they obtained her details.

“He said I had registered my Microsoft product,” said Mandy, “which was correct but I had not provided any contact number.

“And when I pointed this out and demanded to know how he got hold of my number he became very cagey and I know that, under the law, companies who contact you must tell you how they got your number.

“This was clearly a scam, so I kept asking him questions until he eventually gave up.”

Mandy has said people need to be vigilant about what details they pass onto others on the phone.

She added: “Companies like Microsoft have millions of customers and do not contact people out of the blue like this.

“They deliberately target the most vulnerable people and they do sound very convincing - the guy that called me sounded like he was in an actual call centre, but it is all just a trick.

“You should not pass over any details to anyone who rings you out of the blue no matter what they say.”

A spokeswoman for Microsoft advised anyone who thinks they may have been victim of a phone scam to change all their computer’s passwords, including email accounts, banking sites and especially bank and credit card log in details.

She also advised scanning your computer with Microsoft Safety Scanner and to contact bank and credit card companies if you are concerned you may have been a victim.

She said: “We would like to remind users of Microsoft software that the company does not keep track of consumers that purchase their software and does not directly contact consumers for any reason whatsoever.

“Do not trust any caller claiming to be from Microsoft and needing access to your home PC. We do encourage people to keep safe when online and to always ensure the copy of Windows they are running is genuine and fully up to date.