For scammers, the telephone has become a conduit into victims' computers.
Of 7,000 computer users recently surveyed by Microsoft in the U.S., U.K., Canada and Ireland, 15 percent reported having received a phone call from someone posing as a security expert, asking for remote access to computers or money for bogus security products.
Of those who received such a call, 22 percent were successfully tricked by the scammer.
More than 79 percent said they lost money as a result of this deception, with the average loss being $875. Further financial loss was suffered by users who had to have their compromised computers professionally serviced.
Microsoft has advised users to double-check that security software and updates are installed. However, computer security software will not necessarily thwart scammers who convince users to authorize intrusions, conceded Microsoft's Director of International, Public and Analyst Relations, Richard Saunders.
Saunders warned users to beware of increasingly common "tactics of deception" used by hackers.
Recently, Macintosh users were targeted by a similar scam. But rather than placing phone calls, these hackers harvested credit card numbers by infiltrating computers with malware directing users to protect their systems by purchasing security software.