Virus alert about the W32.Lirva.A@mm worm

W32.Lirva.A@mm is a new e-mail worm. The Microsoft Product Support Services Security team is issuing this alert to advise customers to be aware of this virus as it spreads in the wild. If you use best practices, such as filtering certain file types and applying security patches, you can prevent infection from this mass-mailer worm.

Note By default, Microsoft Office Outlook 2003 and Microsoft Office Outlook 2007 provide protection against the W32.Lirva.A@mm mass-mailer worm.

Impact of attack

Mass-mailing, Termination of Antivirus Programs and Firewalls, and Compromise of Cached Passwords

Technical details

W32.Lirva.A@mm is a new mass-mailer worm that also propagates through shares and peer-to-peer file-sharing applications. The W32.Lirva.A@mm worm arrives in an e-mail message that has the following characteristics:

Note The contents vary. The following message is only one example. The worm tries to exploit a previously patched vulnerability that exists in some versions of Microsoft Outlook, Microsoft Outlook Express, and Microsoft Internet Explorer. This vulnerability can be used to allow an executable attachment to run automatically, even if you do not double-click the attachment. For more information about this vulnerability, visit the following Microsoft Web site: Upon execution, the worm tries to disable some antivirus and firewall applications that may be running on the computer. The worm also does one or more of the following:

• Adds entries to the registry
• Copies itself to the system folder
• Sends itself to address book entries
• Collects cached passwords, and then sends them to the attacker

For more detailed information about the W32.Lirva.A@mm worm, contact your antivirus vendor.

Prevention

1. Block potentially damaging attachment types at your Internet mail gateways.
2. Because this virus uses a previously announced vulnerability as part of its infection method, make sure that your computers are patched for the vulnerability that is identified in Microsoft Security Bulletin MS01-020. For more information about this bulletin, visit the following Microsoft Web site:
   http://www.microsoft.com/technet/security/bulletin/MS01-020.mspx
   To obtain the most recent cumulative security patch for Microsoft Internet Explorer, which includes the fixes for the vulnerabilities that were announced in Microsoft Security Bulletin MS01-020, visit the following Microsoft Web site:
   http://www.microsoft.com/technet/security/bulletin/MS02-023.mspx
3. If you are using Microsoft Outlook 2000 Service Release 1 (SR1) or earlier, install the Outlook E-mail Security Update patch to prevent this virus (and the majority of other viruses that are borne by e-mail messages) from running.
   
   Microsoft Outlook 2000 Service Pack 2 (SP2) and Outlook 2002 automatically contain the functionality in the Outlook E-mail Security Update patch.
   
   To install the Outlook E-mail Security Update patch for Outlook 2000 SR1 or earlier, visit the following Microsoft Web site:
   http://www.microsoft.com/downloads/details.aspx?FamilyID=96DF48A9-7638-429E-816E-35F16F6528CA&displaylang=EN
4. Configure Microsoft Outlook Express 6 to block access to potentially damaging attachments. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
   291387 OLEXP: Using virus protection features in Outlook Express 6
   Earlier versions of Outlook Express do not contain attachment-blocking functionality. Use caution when you open unsolicited e-mail messages with attachments.
5. Use a program-level firewall to protect yourself from being infected with this virus through Web-based e-mail programs.

Recovery

If your computer has been infected with this virus, contact Microsoft Product Support Services or your preferred antivirus vendor for help with removing the virus. For information about how to contact Microsoft Product Support Services, visit the following Microsoft Web site

Related security information

For additional information about viruses, visit the following third-party Web sites: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

For additional security-related information about Microsoft products, visit the following Microsoft Web site: