Microsoft has touted Vista as a more secure version of Windows, but on the day of Vista\u2019s official launch, a security company has identified malware already in circulation that can infect computers running the OS.Sophos identified three viruses typically spread through e-mail that can infect Vista customers who use a third-party Web e-mail client. While Vista\u2019s e-mail client stops Stratio-Zip, Netsky-D and MyDoom-O, the malware slips past Vista\u2019s defenses when users receive infected messages through a Web-based e-mail service, Sophos said. Stratio-Zip topped Sophos\u2019 list of malware affecting computer users in November, accounting for 33.3 percent of malware in circulation. Combined, the three viruses that can affect Vista users make up 39.7 percent of all malware in circulation during the month, Sophos said. However, even if the malware Sophos identified slips through in an e-mail, customers won\u2019t necessarily be affected, another researcher said. Additional Vista security mechanisms should protect users, said Mikko Hypponen, chief research officer at F-Secure. If a customer opens an infected malware file, Vista would warn and question the user before allowing the malware to wreak havoc. "These particular examples of malware probably wouldn\u2019t still be able to successfully infect the machine unless the user specifically allows it," he wrote in an e-mail exchange. Sophos applauded the security improvements in Vista, saying that the variety of popular third-party applications used by consumers inevitably will open doors to hackers.Other antivirus companies haven\u2019t been so kind. McAfee has been highly critical of changes in the operating system that it says will make Vista less secure than previous versions of Windows. Symantec said it has discovered vulnerabilities in Vista\u2019s networking software\u00a0that make it less stable than Windows XP. Sophos found that overall, the proportion of infected e-mail remained low in November at 0.28 percent, but identified a record number of new threats, 7,612, during the month.-Nancy Gohring, IDG News Service (Dublin Bureau)Related Link:Microsoft Windows Vista: The OS Has LandedCheck out our CIO News Alerts and Tech Informer pages for more updated news coverage.