O97M.Shiver.A

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Discovered: September 03, 1998
Updated: February 13, 2007 11:34:04 AM
Also Known As: W97M/X97M.Shiver.A
Type: Virus


This virus affects Microsoft Word and Excel documents.

Antivirus Protection Dates

  • Initial Rapid Release version December 19, 2000
  • Latest Rapid Release version December 19, 2000
  • Initial Daily Certified version December 19, 2000
  • Latest Daily Certified version December 19, 2000

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Raul Elnitiarta

Discovered: September 03, 1998
Updated: February 13, 2007 11:34:04 AM
Also Known As: W97M/X97M.Shiver.A
Type: Virus


The basic set of modules is:

    • Module1
    • Macro1
    • Sentry
It contains several sub-functions to intercept MS Word and MS Excel menu:
    • AutoOpen
    • AutoExec
    • AutoExit
    • ToolsMacro
    • ToolsOptions
    • FileTemplates
    • ViewVBCode
    • Auto_Open
    • Auto_Close

The infection mechanism is similar to O97M.Teocatl. AutoOpen performs the infection in MS Word while Auto_Open performs the infection in MS Excel. The other sub-functions intercept MS Word and MS Excel menu without doing anything. The cross-infection routine works as described below.

While exiting from MS Word, the virus checks if MS Excel is running. If MS Excel is not running, it minimizes MS Word, deletes PERSONAL.XLS from XLSTART directory, and loads MS Excel in minimized state. This is quite noticeable in slower system since both MS Word and MS Excel are shown in the taskbar while the virus does its cross-infection routine. The virus then creates a Macro1 module in a new PERSONAL.XLS.

Similarly, while closing an infected MS Excel file, it checks if MS Word is running, loads MS Word in minimized state, and creates Module1 into NORMAL.DOT.

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.

Writeup By: Raul Elnitiarta