Redmond (WA) - Microsoft released first details about the impact of its Windows Malicious Software Removal Tool (MSRT), which claim that the company has removed 16 million "instances" of malware on a total of 5.7 million computers since it was launched in January of last year.

According to the data published, the MSRT was run by "at least" 270 million users approximately 2.7 billion times on systems based on Windows 2000, Windows XP, and Windows Server 2003. On average, the tool removed at least one potential threat from every 311 computers it runs on, Microsoft said.

Microsoft says that the data collected indicates that backdoor trojans, which allow an attacker to take control of an infected computer, are a "significant and tangible threat to Windows users." Out of the 5.7 million computers that were detected to carry infections, approximately 3.5 million or 61% had a backdoor trojan on their hard drives. Bots, a sub-category of trojans that use Internet Relay Chat techniques, represented a majority of those threats, Microsoft said.

The MSRT also encountered rootkits on 14% of infected PCs. Microsoft currently considers these intruders, which typically hide malicious components on a PC a "potential emerging threat."

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