A new wave of malicious emails containing a fake Microsoft Windows security update began hitting inboxes in an effort to spread malware, researchers at anti-virus firm Sophos have warned. The messages, which appear to be sent from Microsoft's security team and contain the subject line "Update your Windows," advise users to update their operating system by downloading an attached executable file, Graham Cluley, senior technology consultant at Sophos, wrote in a blog post Tuesday. The attached file, called "KB453396-ENU.zip," is actually an AutoRun worm. Users should be advised that Microsoft never distributes security updates via email attachments, Cluley said. - AM