A Trojan horse masquerading as a tool that helps users get ready for Windows 7 is on the loose and about to become widespread, a security firm said today.

According to a report by researchers at BitDefender, the new attack seeks to take advantage of users who are anxious to move over to the new Microsoft operating system, which is scheduled for general availability in October.

"This piece of software supposedly allows them to see if their system resources could support the new OS," BitDefender says. "All they have to do is open the attached .zip file.

"Instead of the promised compatibility checking tool, the zip file hides Trojan.Generic.3783603. This piece of malware contains malicious or potentially unwanted software, which it drops and installs on the system. Frequently, it installs a backdoor, which allows remote, clandestine access to the infected system. This backdoor may then be used by cybercriminals to upload and install additional malicious or potentially unwanted software on the captured system."

Early statistics indicate that a "massive spreading" of the Trojan is about to begin, BitDefender says. "Although this phenomenon has just started, it seems that it's just a matter of time before the cybercriminals control a huge number of systems," the researchers say.

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