SEATTLE – Many Windows PCs have been turned into zombies, but rootkits are not yet widespread, according to a Microsoft security report just released.
More than 60 percent of compromised Windows PCs scanned by Microsoft’s Windows Malicious Software Removal Tool between January 2005 and March 2006 were found to be running malicious bot software, CNET News.Com reported. The tool removed at least one version of the remote-control software from about 3.5 million PCs, it added. That’s compared with an overall 5.7 million machines with infections overall.
“Backdoor Trojans?are a significant and tangible threat to Windows users,” Microsoft said in the report.
A computer compromised by such a Trojan horse, popularly referred to as a zombie PC, can be used by miscreants in a network of bots, or “botnet”, to relay spam and launch cyberattacks. Additionally, hackers often steal the victim’s data and install spyware and adware on PCs, to earn a kickback from the spyware or adware maker.
Microsoft introduced the Windows Malicious Software Removal Tool in January last year. An updated version of the program ships monthly with Microsoft’s security updates. The tool aims to identify and remove prevalent malicious software from PCs. Since its release, it has run about 2.7 billion times on at least 270 million computers, Microsoft said.
Over the 15-month period covered by the report, the tool found that 5.7 million of unique Windows systems were infected. It removed 16 million instances of malicious software from these systems, Microsoft said.
Backdoor Trojans are the most prevalent threat, followed by e-mail worms, which were found on and removed from just over 1 million PCs, Microsoft said. Rootkits, which make system changes to hide another piece of possibly malicious software, are less widespread, with removals from 780,000 PCs.
“Rootkits?are a potential emerging threat but have not yet reached widespread prevalence,” Microsoft said in the report. This contrasts with a study from McAfee, which in April said the numbers of rootkits it sees are rising sharply.
Rootkits lunged into the public spotlight last year when anticopying software on certain Sony BMG Music Entertainment CDs was found to contain a rootkit. Microsoft added detection and removal capabilities for the Sony rootkit in December, and its tool wiped off the software 250,000 times, according to the report.
