Windows Vista is wide open to nearly 40 percent of the malware currently circulating, Microsoft has admitted, following a report by Sophos.Remarkably, with the new operating system just released to business, the software giant said in effect that there is nothing it can do about the threats in question\u2014Stratio-Zip, Netsky-D and MyDoom-O\u2014because they rely on social engineering to invade systems. The three threats together account for 39.7 percent of circulating malware, according to Sophos."Based on our initial investigation, Microsoft can confirm that these variants do not take advantage of a security vulnerability; rather, they rely on social engineering to infect a user\u2019s system," Microsoft said in a statement.While the e-mail system built into Vista, Windows Mail Client, stops all of the top 10 viruses identified by Sophos for November, the three threats outlined can infect systems when a third-party e-mail client is used, Sophos said last week. Stratio-Zip was November\u2019s top malware, accounting for one-third of virus traffic, Sophos said.Sophos said that while no Vista-specific viruses have yet been detected, they are likely to appear soon. "It won\u2019t be long before cybercriminals develop Vista-specific malware or modify current threats to fit the bill," said Ron O\u2019Brien, Sophos senior security analyst, in a statement. "The Stratio-Zip worm, for example, remains on the top ten list due to constant, minor alterations to its code that force security systems to re-identify the malware."Few actual installations of Vista currently exist, since the OS was launched\u00a0this past\u00a0Thursday. Sophos and McAfee have antivirus products ready for Vista, but Symantec, Trend Micro and CA are still working on theirs.Microsoft congratulated itself on the "aggressive security design decisions" it took with Windows Mail Client, but said if users choose to use other, more vulnerable e-mail programs, they can configure User Account Control to help limit the damage users can cause if they\u2019re infected.-Matthew Broersma, Techworld.com (London)\n\nMicrosoft Windows Vista: The OS Has Landed\n\nSophos: Windows Vista Users May Be Affected by Existing MalwareCheck out our CIO News Alerts and Tech Informer pages for more updated news coverage.