WM.MDMA

SUMMARY

WM.MDMA is a modified version of the DMV macro virus. WM.MDMA uses only one macro, AutoClose, and therefore infects the global template when infected documents are closed. If the global template is infected, documents are infected as they are closed.

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
• Payload Trigger: First day of every month
• Deletes Files: C:SHMK (all files) C:WINDOWS (all help files) C:WINDOWSSYSTEM (all Control Panel files)

Distribution

• Distribution Level: Low
• Target of Infection: Global Template, Hard drive, Microsoft Word documents

TECHNICAL DETAILS

On the first day of every month (for example, March 1, April 1, June 1), WM.MDMA unsuccessfully checks the platform it is running on and attempts to delete files on the user’s system. Because of a bug in the code, the virus always assumes it is running on a Windows 95 system. If the day is correct, WM.MDMA attempts to delete files in the following directories:

• C:SHMK (all files)
• C:WINDOWS (all help files)
• C:WINDOWSSYSTEM (all Control Panel files)

These commands are unsuccessful on Macintosh platforms, but have a high probability of deleting at least some files on PCs running DOS, Windows 3.1, Windows 95, or Windows NT.

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.