Discovered: January 10, 2001
Updated: February 13, 2007 12:46:51 PM
Type: Macro
Systems Affected: Mac, Windows

X97M.Sufe is a macro virus that infects Microsoft Excel spreadsheets. It replicates by exporting the entire viral module to a file named C:\Ms_io.sys, and then importing it to new spreadsheets. This macro virus has a payload that can be executed twice each month.

Antivirus Protection Dates

  • Initial Rapid Release version January 10, 2001
  • Latest Rapid Release version January 10, 2001
  • Initial Daily Certified version January 10, 2001
  • Latest Daily Certified version January 10, 2001

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

Writeup By: Neal Hindocha

Discovered: January 10, 2001
Updated: February 13, 2007 12:46:51 PM
Type: Macro
Systems Affected: Mac, Windows

X97M.Sufe infects Microsoft Excel spreadsheets. When this virus is executed on a computer for the first time, it immediately changes the following Microsoft Excel options:

  • UserName = "SUFE"
  • AltStartupPath = "C:\MS_DOS"
  • EnableSound = False
  • RollZoom = False

The virus verifies that the Command.dos file exists in the C:\Ms_dos folder. If it does not, the virus creates both the folder and the file. The Command.dos file contains the macro module.

The following is the replication routine that it uses to spread:
  1. The virus replicates by importing itself from a file that it creates (C:\Ms_io.sys) to spreadsheets that are not infected. The following comments can appear at the top of the viral macro module:

    '\Hello!Be sure to make good use of this piece of virus code.Good luck!
  2. The virus uses these comments as an infection checker. If the comments are not found, the virus carries out the replication.
  3. Finally, this virus executes a function it calls "punish." This function contains the payload. The payload is date and day triggered, and it will be executed only if the following are true:
    • It is the first day or the tenth day of the month.
    • The day is a Saturday or a Sunday.

The payload clears the entire spreadsheet, changing several options and inserting "junk" in various fields.

The virus contains a function that is executed only when closing a spreadsheet. This function will look in the same folder that contains the spreadsheet for other Microsoft Excel spreadsheets. If it finds any, this virus will attempt to infect them.


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: Neal Hindocha

Discovered: January 10, 2001
Updated: February 13, 2007 12:46:51 PM
Type: Macro
Systems Affected: Mac, Windows

To remove this virus, do all of the following:

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Run a full system scan. If any files are detected as infected with X97M.Sufe, choose Repair.
  3. Use Windows Explorer to look for the following files, and delete them if they are found:
    • C:\Ms_io.sys
    • C:\Ms_dos\Command.dos

Writeup By: Neal Hindocha