Experts are warning of a sharp rise in the number of malware infections caused by rogue security programs.
Trend Micro has reported a fivefold year-on-year increase in the use of such programs, which claim to clean a computer system but end up infecting users.
Typically a user will visit a web page that includes a pop up warning that their computer is infected and offering a free trial of software to clean up the computer.
Suspect software includes Winfixer, SpywareQuake, ErrorSafe, ErrorGuard, SpyShield, ApyAxe, SpywareNuker and, most recently, Spyhealer, DriverCleaner and SystemDoctor.
"Rogue security programs are clearly on the rise, and users must demonstrate caution and always be alert when downloading software," said George Moore, threat researcher at Trend Micro.
"In addition they need to protect their systems by using the latest security software against web threats from a known and reliable vendor."
In many cases the rogue security software contains a fresher version of the malware and, if subscribed to, will not perform an effective security scan.
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