Phishers posing as computer security experts are targeting individuals and businesses to steal money and install malicious software on their computers.
In a survey of 7,000 people, 15 percent across the UK, US, Ireland and Canada reported receiving a call from scammers, Microsoft said on Thursday. Of these, 22 percent had been deceived by the phishers and so lost money.
"The scam works by criminals posing as computer security engineers and calling people at home to tell them they are at risk of a computer security threat," Microsoft said. "The scammers tell their victims they are providing free security checks and add authenticity by claiming to represent legitimate companies and using telephone directories to refer to their victims by name."
The best way for people to protect themselves is to keep their computer's security software up to date and to be suspicious of unsolicited calls.
Once trust has been established, the scammers attempt to make the victim think there's something wrong with their computer. They then trick them into downloading software that gives hackers remote access to their computer.
The "vast majority" of individuals scammed in this way suffered some sort of financial loss, Microsoft said. Also, those affected carry a further cost; as they then have to repair the damage caused to their computers by the hackers, the costs of which can range between $1,730 (£1,068) and $4,800.
At the moment, the scam appears to only operate in countries where the predominant language is English, however Microsoft's director of international public relations, Richard Saunders, believes it will broaden out to other languages.
"Fake lottery scams and other forms of internet scams have followed this pattern," he said.