W97M.Ethan.A

SUMMARY

W97M.Ethan.A is a macro virus.

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: While closing an infected document, the virus, with 30% chance, modifies the following File Summary Information fields: Title = "Ethan Frome" Author = "EW/LN/CB" Keywords = "Ethan" File Summary Information is accessible from File-Properties menu in MS Word 97. This macro virus also removes the temporary text file "C:CLASS.SYS" that most W97M.Class variants use.
• Deletes Files: Class.sys

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

This MS Word 97 macro virus inserts its viral code to the beginning of "ThisDocument" VBA module. "ThisDocument" is a default module in MS Word 97 template that is not listed in Tools-Macro macro list.

While infecting a document or global template, this macro virus uses a temporary text file "C:ETHAN.___" The virus marks this temporary text file as hidden-system file.

The first report of this macro virus from the field came to Symantec AntiVirus Research Center on January 12, 1999 through Norton Anti-Virus Scan-and-Deliver system.

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

Although the temporary text file " C:ETHAN.___" is harmless, deleting it is recommended.

Because this macro virus insert its viral code into "ThisDocument" module, any code that has previously been entered to "ThisDocument" module will need to be re-entered after NAV repair the file.