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Discovered: August 14, 2001
Updated: February 13, 2007 11:47:17 AM
Also Known As: W32/Modnar
Type: Worm

W32.Modnar.Worm@mm is a mass-mailing worm that appears to be written in C++. When executed, the worm extracts all of the email address from the Windows Address Book (WAB). The worm then emails a copy of itself to all of the extracted email addresses.

What are Portable Executable (PE) files?
PE files are files that are portable across all Microsoft 32-bit operating systems. The same PE-format executable can be run on any version of Windows 95, 98, Me, NT, and 2000. All PE files are executable, but not all executable files are portable.

Antivirus Protection Dates

  • Initial Rapid Release version August 14, 2001
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version August 14, 2001
  • Latest Daily Certified version August 09, 2016 revision 001

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

Writeup By: Neal Hindocha

Discovered: August 14, 2001
Updated: February 13, 2007 11:47:17 AM
Also Known As: W32/Modnar
Type: Worm

When executed, the worm W32.Modnar.Worm@mm creates a copy of itself in the same folder. The name of the file that it creates is random, but always has the extension .doc.pif. Some examples of file names are:

  • Nbgmcknc.doc.pif
  • Dhjgktjm.doc.pif
  • Wsyrlmzu.doc.pif

It next attempts to send the copy to everyone in the Windows Address Book (WAB). However, the email routine requires an active MAPI session. Therefore, for the worm to send itself out you must be logged in to a MAPI-compliant email program, such as Microsoft Outlook.

The worm does not modify any files on the system, nor does it add or modify any registry keys. If the worm is executed a second time, it will create another copy of itself and attempt to email this copy to everyone in the WAB.

All samples that we have received have been packed with a known runtime compression program that is used for Portable Executable (PE) files. The size of the worm, when uncompressed, is approximately 180 KB.


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: August 14, 2001
Updated: February 13, 2007 11:47:17 AM
Also Known As: W32/Modnar
Type: Worm

Run LiveUpdate to make sure that you have the most recent virus definitions.

  1. Start Norton AntiVirus (NAV), and run a full system scan. Be sure that NAV is configured to scan all files.
  2. Delete all files that are detected as W32.Modnar.Worm@mm.

Writeup By: Neal Hindocha