And, says the IT security specialist, the numbers of PCs infected with fake anti-virus may run into tens of millions worldwide.
In its study on rogue security software, Symantec analyzed data from internet users over a 12 month period to June 2009 and found that cybercriminals are increasingly planting fake security alerts that pop up when computer users access a legitimate website.
The `alert', said Symantec, warns users of a virus and offers security software such as anti-virus, sometimes for free and sometimes for a fee.
"Lots of times, in fact they're a conduit for attackers to take over your machine", said Vincent Weafer, Symantec's vice president for security response.
"They'll take your credit card information, any personal information you've entered there and they've got your machine", he said, referring to the fake anti-virus software's ability to snare a users' machine into a botnet.
In its research, Symantec found 250 varieties of scam security software such as fake anti-virus with legitimate-sounding names like Antivirus 2010 and SpywareGuard 2008, and about 43 million attempted downloads in one year but did not know how many of the attempted downloads succeeded.
"In terms of the number of people who potentially have this in their machines, it's tens of millions", Weafer said.
It was also impossible to tell how much cybercriminals made off with but `affiliates' acting as middlemen to convince people to download the fake anti-virus software were believed to earn between IS$0.01 per download and $0.55.
According to Weafer, one site, TrafficConverter.biz, which has now been shut down, had boasted that its top affiliates earned as much as $332 000 a month for selling scam security software.
"What surprised us was how much these guys had tied into the whole affiliated model", Weafer said. "It was more refined than we anticipated."