W97M.Mxfile.L.gen

SUMMARY

W97M.Mxfile.L.gen is a simple macro virus which spreads by infecting Microsoft Word documents and the global template, Normal.dot.

Protection

• Virus Definitions (LiveUpdate™ Weekly) May 15, 2002
• Virus Definitions (Intelligent Updater) May 15, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Modifies Files: Targets Microsoft Word .doc and .dot files.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When a document that is infected with W97M.Mxfile.L.gen is opened or closed, the macro virus performs the following actions:

1. It changes several Microsoft Word options so that:
   • The screen updating is turned off to speed up the macro code. You cannot see what the macro is doing, but it runs faster.
   • When you open a document that contains a macro, the default warning message no longer appears.
   • When you exit Microsoft Word, any changes that were made to the Normal.dot template are automatically saved without prompting you.
   • When you open a file that is not a Word document or template, the Convert File dialog box does not appear.
2. It infects all active documents and the Normal.dot template file with the MXFILE viral macro module.
3. On certain days the macro virus may insert some text into the document. The language of the that text is not detected.
4. It hooks some menu commands. For example, it disables the Macro command on the Tools menu.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate. LiveUpdate is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. If NAV detects any files infected by W97M.Mxfile.L.gen, click Repair.