WM.ShareFun.A

SUMMARY

WM.ShareFun.A is a macro virus that infects MS Word 7 and Word 8 documents and templates. The virus contains 9 macros: AutoExec, AutoOpen, FileExit, FileOpen, FileSave, FileClose, ToolsMacro, FileTemplates and ShareTheFun.

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: Opening infected file.
• Large Scale E-mailing: Randomly emails 3 MS Mail recipients. Email subject "You have GOT to read this!"

Distribution

• Distribution Level: Low
• Target of Infection: Microsoft Word documents, MS Mail, Operating system.

TECHNICAL DETAILS

The AutoOpen macro is responsible for copying macros to and from the global template. When an infected file is opened, the macros are copied from the infected document into the global template. The virus infects other documents by way of the following FileTemplates macros:

• FileExit
• FileOpen
• FileSave
• FileClose
• ToolsMacro

When any of these macros are run they call the macro copying function in AutoOpen to copy the macros from the global template to the document.

When an infected document is opened, then virus will randomly call the ShareTheFun macro which saves the infected document to the root directory as "doc1.doc." It then looks for a running copy of Microsoft Mail. If MS Mail is not running the virus will shutdown Windows entirely. If it does find a copy of MS Mail running it will switch to that application and randomly pick three names from the address book and send them an email that has the infected document attached. The message will be empty but it will have the title "You have GOT to read this!." After sending the mail, the virus closes MS Mail. If anyone receives this message and opens the attached document they will also become infected.

The Symantec AntiVirus Research Center (SARC) would like to make clear that this virus implements techniques to automatically spread only in MS Mail clients. Additionally, those who are not actively running MS Mail at the time the virus triggers will not automatically spread the virus.

This virus has been reported only in a single site, is not considered in wide distribution and does not pose an immediate threat to the public. (February 24, 1997).

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.