W97M.WMVG.Gen

The virus generator has many options. Norton AntiVirus detect any macro virus that has been generated with this kit. The viruses can have different payloads and use different methods to spread.

The virus changes the following in Microsoft Word:

• It disables the warning message that appears by default when you open a document that contains macro.
• Any changes made to the Normal.dot template are automatically saved without prompting when Microsoft Word closes.
• When you open a file that is not a Word document or template, the Convert File dialog box does not appear.
• The status bar is disabled.
• When you open a file, a message recommending that the file be opened as read-only is not displayed.
• If you are using Microsoft Word 2000, security is set to the lowest level so that Word will run all the macros without prompting. The menu option responsible for the security level is disabled.
• The Alt+F11 key combination is disabled. This prevents you from invoking the Visual Basic Editor when the key combination is pressed.

The virus replicates either by infecting the active document and the Normal.dot template directly, or through the temporary file C:\Windows\Username.sys.

The following options can be present in the family of W97M.WMVG.Gen macro viruses:

• If you join an IRC channel which an infected user has already joined, you will receive the ReadMe.doc file from the infected user. This file is the W97M.WMVG.Gen replicate, and it is stored in the local folder C:\Mirc\Download. You will then join the channel #virus with the nickname "Im Infected With A Virus Created By WMVG" to let the virus author know how many users are infected.
• The virus drops the Visual Basic Script Backup.vbs into the C:\Windows\ folder. It creates the value
  
  C:\Windows\Backup.vbs
  
  in the registry key
  
  HKEY_LOCAL_MACHINE\Software\Microsoft\
  Windows\CurrentVersion\Run\WMVG
  
  This ensures that the script will run every time that Windows starts. When executed, the script changes the security settings of Word. It then infects the Normal.dot template with a code from the temporary file C:\Windows\Backup.drv.

Depending on the options selected, the generated macro virus may have one of the following payloads:

• It may display a custom message box.
• The virus may attempt to open and close the CD-ROM drive continuously and change the system palette to random colors.
• It may delete the active document and then invoke the Office Assistant, using settings defined by the virus creator.

The payload trigger, like the payload itself, is determined by the virus creator.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• 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.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. 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.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
• For further information on the terms used in this document, please refer to the Security Response glossary.

Summary