W97M.Seqnum

SUMMARY

This somewhat polymorphic W97M virus infects documents using Document_Open, and document templates using Document_Close. It stores an integer number in a file property variable in the VBA5 module properties. In the document infection, this variable is named "seqNum" in the macro code. During infection, a file is inserted with a name based on the following convention:

[Application.Path][seqNum].BAS

where "Application.Path" is the Microsoft Word program folder and "seqNum" is derived from the file property variable. The "seqNum" value gets modified in the inserted file when it exports the source into the "[seqNum].BAS" file

Protection

• Virus Definitions (Intelligent Updater) December 28, 1999

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

TECHNICAL DETAILS

On January 1st, the virus moves C:WINDOWSWIN.INI into a file based on the following variables:

[Application.Path][seqnum]

Note that the renamed WIN.INI file has the same name as the inserted file without the .BAS extension. On Wednesdays, the virus adds the following text into the footer of the infected document:

[seqnum]@hnet.pen

Again, "seqnum" is derived from the file property variable.

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

Infected users should move the [Application.Path][seqnum] file back to the windows folder and rename it to "WIN.INI". Additionally, users may wish to search for, and remove, the "[seqnum].bas" file that is created.