WM.DMV

SUMMARY

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

Distribution

• Distribution Level: Low
• Target of Infection: Microsoft Word documents

TECHNICAL DETAILS

WM.DMV is a macro virus written and published by Joel McNamara in December 1994. In his paper, McNamara outlines the potential of macro viruses and the vulnerability of documents, e-mail and OLE environments. Near the end of his document, McNamara provides complete, commented source code for a fully infectious Document Macro Virus (DMV). In addition to the source code provided, the document itself is intentionally infected. Although the intention of the paper may have been to instruct and advise, McNamara’s paper has been posted on major Internet newsgroups and bulletin board services, and has been used as a tutorial for writing some of the first macro viruses. McNamara has been heavily criticized by prominent members of the anti-virus community for making his paper available to the general public in an unabridged form. Malicious suggestions and replication code found in McNamara’s paper were implemented in the Nuclear macro virus.

WM.DMV uses a single macro, AutoClose, which auto-executes when an infected document is closed. At each stage of infection, the virus displays a message box explaining actions as they are completed. None of the original code is destructive, although suggestions are made as to where destructive commands can be inserted. Dialogs are displayed with the following messages:

Counting global macros.

AutoClose macro virus is already installed in NORMAL.DOT.

Infected NORMAL.DOT with copy of AutoClose macro virus.

AutoClose macro virus already present in this document.

Saved current document as template.

Infected current document with copy of AutoClose macro virus.

Macro virus has been spread. Now execute some other code (good, bad, or indifferent).

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.