WM.Pesan.B

SUMMARY

WM.Pesan.B infects a document with 6 macros:

• AutoOpen
• NormalAuto
• ToolsMacro
• CopyOfFileExit
• CopyOfFileSave
• CopyOfFileSaveAs

It infects the Global Template (NORMAL.DOT) with the same 6 macros in different name:

• CopyOfAutoOpen
• AutoExec
• ToolsMacro

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 27, 1997
• Virus Definitions (Intelligent Updater) June 27, 1997

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: Destructive
• Deletes Files: Delete the entire hard drive
• Modifies Files: Modifies Normal.Dot Global template. Creates companion batch files for several DOS executable utility files. When the DOS executable files are run, the companion batch file attempts to delete all files from the hard drive.

Distribution

• Distribution Level: Low
• Target of Infection: Microsoft Word documents, executable files, all files on hard drive.

TECHNICAL DETAILS

The presence of a macro named ToolsMacro in the infection makes MS Word Tools-Macro menu useless.

• FileExit
• FileSave
• FileSaveAs

The AutoOpen, FileSave and FileSaveAs macros are responsible for spreading the infection in ways similar to infection of WM.Concept.

Destructive Payload:

After global template (NORMAL.DOT) is infected, any subsequent opening of Microsoft Word will execute the AutoExec macro. The AutoExec macro will search in C:DOS directory for several DOS executable utility files and create a companion batch files for each. These companion batch files are of the same name as the original DOS files, but instead of providing a useful operation, they contain one line of destructive instruction that delete all directories and files in C drive.

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

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate. LiveUpdate is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
     
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
   • NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
3. Run a full system scan.
4. If any files are detected as infected by WM.Pesan.B, click Repair.