Revision Note: Advisory published Advisory Summary:Microsoft is aware of the Sober mass mailer worm variant named Win32/Sober.Z@mm. The worm tries to entice users through social engineering efforts into opening an attached file or executable in e-mail. If the recipient opens the file or executable, the worm sends itself to all the contacts that are contained in the system’s address book. Customers who are using the most recent and updated antivirus software are at a reduced risk from infection by the Win32/Sober.Z@mm worm. On systems that are infected by Win32/Sober.Z@mm, the malware is programmed to download and run malicious files from certain Web domains beginning on January 6, 2006. Beginning approximately every two weeks thereafter, the worm is set to begin downloading and running malicious files from additional sites on the same Web domains. As with all currently known variants of the Sober worm, the worm does not appear to target a security vulnerability, but rather relies on the user opening an infected attachment. Microsoft added detection for the latest Sober variants in its December 2005 update to the Malicious Software Removal Tool and in the Windows Live Safety Center. Customers who believe that they are infected with Sober or are not sure whether they are infected should visit Safety.live.com and choose "Protection Scan" or run the latest version of the Malicious Software Removal Tool from either Microsoft Update or Windows Update to ensure that their systems are free of infection. Additionally, Windows OneCare from Microsoft provides detection for and protection against Sober and its known variants. Microsoft will release an updated version of the Malicious Software Removal Tool on January 10, 2006, that will further assist in the detection and removal of known malware threats including Sober and its known variants. See Microsoft Knowledge Base Article 891716 for additional details on how to deploy the Malicious Software Removal Tool with the latest definitions to help protect against malware. For mor

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