REDMOND, WA – In a report published on Monday, Microsoft Corp. detailed conclusions derived from research conducted by a “dedicated Antimalware team” created by the software giant in response to the growing threat of malware and other “potentially unwanted software.”Much of the data has been collected by way of the Windows Malicious Software Removal Tool (“MSRT”), which Microsoft first delivered in January of 2005 to users running Microsoft Windows 2000, Windows XP, and Windows Server 2003. The MSRT was made available in 24 different languages initially and Microsoft reports that the company has “shipped 15 additional, enhanced versions” of the tool and plans to issue a new version on the second Tuesday of each month, with each update “adding new prevalent malware to detect and remove.”

According to Microsoft, since the MSRT was first shipped, the tool has been “executed approximately 2.7 billion times by at least 270 million unique computers.”

Among the conclusions published in Microsoft’s malware report, the Microsoft anti-malware team found that “Backdoor Trojans,” which can allow an attacker to control infected computers remotely, “are a significant and tangible threat to Windows users..

“The MSRT has removed at least one backdoor Trojan from approximately 3.5 million unique computers,” Microsoft states in the report. “Thus, of the 5.7 million unique computers from which the tool has removed malware, a backdoor Trojan was present in 62-percent of computers. Bots, a sub-category of backdoor Trojans which communicate through the Internet Relay Chat (IRC) network, represent a majority of the removals.”

The research team found that “rootkits,” another likely source of malicious code, are less prevalent than some analysts had feared. The report states that rootkits are “potential emerging threat but have not yet reached widespread prevalence.”

“Of the 5.7 million unique computers that the tool has removed malware from, a rootkit was present in 14-percent of the cases,” the report states, adding that the number drops to nine percent if the “WinNT/F4IRootkit,” the rootkit distributed on Sony music CDs (and which generated much controversy and backlash for Sony), is removed from the calculations.

Noting that the “malware problem appears to be migratory in nature,” Microsoft’s report also identified “social engineering attacks” as a “significant source of malware infections.”

“Worms that spread through e-mail, peer-to-peer networks, and instant messaging clients account for 35-pecent of the computers cleaned by the [MSRT] tool,” the report states.

Microsoft says that by releasing and maintaining the MSRT it has “two main objectives;” the first objective is to “reduce the impact of prevalent malicious software on Windows users,” and the second is to “use the data collected by the MSRT to assemble a reliable set of trends on the malicious software actually affecting Windows customers today.”

The company also emphasized that the MSRT “does not target spyware and potentially unwanted software.”

“Windows users should download and install an up-to-date antispyware application to detect and remove spyware and potentially unwanted software from their computers,” Microsoft states in the malware report. “We highly recommend that Windows users install and maintain an up-to-date antivirus solution offering real-time protection and a complete antivirus signature database.”