Revision Note: Additional information about the blank password restriction functionality in Windows XP Service Pack 1, Windows XP Service Pack 2, Windows Server 2003, and Windows Server 2003 Service Pack 1. Added link to Virus Information Alliance member Sophos. Advisory Summary:Microsoft wants to make customers aware of the Mywife mass mailing malware variant named Win32/Mywife.E@mm. The mass mailing malware tries to entice users through social engineering efforts into opening an attached file in an e-mail message. If the recipient opens the file, the malware sends itself to all the contacts that are contained in the system’s address book. The malware may also spread over writeable network shares on systems that have blank administrator passwords. Customers using Windows XP Service Pack 1, Windows XP Service Pack 2, Windows Server 2003, or Windows Server 2003 Service Pack 1 may be at reduced risk from this malware; if the account password is blank, the account is not valid as a network credential. In an environment where you can guarantee physical security, you do not need to use the account across the network, and you are using Windows XP or Windows Server 2003, a blank password is better than a weak password. By default, blank passwords can only be used locally in Windows XP and Windows Server 2003. Customers who are using the most recent and updated antivirus software could be at a reduced risk of infection from the Win32/Mywife.E@mm malware. Customers should verify this with their antivirus vendor. Antivirus vendors have assigned different names to this malware but the Common Malware Enumeration (CME) group has assigned it ID CME-24. On systems that are infected by Win32/Mywife@E.mm, the malware is intended to permanently corrupt a number of common document format files on the third day of every month. February 3, 2006 is the first time this malware is expected to permanently corrupt the content of specific document format files. The malware also modifies or deletes files and registry keys associated with certain computer security-related applications. This prevents these applications from running when Windows starts. For more information, see the Microsoft Virus Encyclopedia.As with all currently known variants of the Mywife malware,

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