X97M.Laroux.TY

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Updated: February 13, 2007 12:11:37 PM
Type: Macro


This virus infects Microsoft Excel 97 spreadsheets. The virus does not contain a malicious payload. It disables the Microsoft Excel macro virus protection option and removes the Microsoft Excel macro toolbar from the Tools menu.

Antivirus Protection Dates

  • Initial Rapid Release version July 21, 2000
  • Latest Rapid Release version July 21, 2000
  • Initial Daily Certified version July 21, 2000
  • Latest Daily Certified version July 21, 2000

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

Writeup By: Eric Chien

Updated: February 13, 2007 12:11:37 PM
Type: Macro


This Microsoft Excel 97 macro virus adds a Visual Basic Application (VBA) module into open spreadsheets.

The infection routine is triggered when a file is opened. Upon execution, the virus attempts to modify the registry key:

HKLM\Software\Microsoft\Office\8.0\Excel\Microsoft Excel\Options6

The virus disables the Microsoft Excel macro virus protection option. It also removes the macro toolbar from the Tools menu.

This macro virus creates a Personal.xls file in the Excel Startup folder (usually office\XLStart). This loads the viral code every time Excel is opened.

The virus is polymorphic and changes the module name upon infecting the Personal.xls. The module always has a two-character name. The module name does not change when infecting documents, only when infecting Personal.xls.

When infecting, the virus checks whether the spreadsheet is already infected. This prevents the virus from infecting a file twice

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: Eric Chien

Updated: February 13, 2007 12:11:37 PM
Type: Macro


To enable macro virus protection in Excel:
1. Click Tools Options General .
2. Click Macro virus protection .

To restore the Excel macro Tool menu:

1. Click Tools Customize Commands.
2. Click Tools.
3. Drag the Macros... option from the right-hand side to the appropriate menu.

Writeup By: Eric Chien