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Discovered: September 03, 2001
Updated: February 13, 2007 11:37:12 AM
Also Known As: I-Worm.Magistr.b [Kaspersky], W32.Magistr.B@mm, W32/Magistr.b@MM [McAfee], W32/Magistr.32768@mm [Frisk], PE_Magistr.B [Trend], W32/Magistr-B [Sophos], Win32.Magistr.29188 [Computer
Type: Worm, Virus
Systems Affected: Windows

Due to a decreased number of submissions, Symantec has downgraded this virus to a Category 2 rating on October 29, 2003.

The W32.Magistr.39921@mm worm is a variant of W32.Magistr.24876@mm .

Antivirus Protection Dates

  • Initial Rapid Release version September 04, 2001
  • Latest Rapid Release version November 04, 2019 revision 019
  • Initial Daily Certified version September 04, 2001
  • Latest Daily Certified version November 04, 2019 revision 065
  • Initial Weekly Certified release date September 04, 2001

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

Technical Description

A list of the additional features and behavioral differences between W32.Magistr.39921@mm and W32.Magistr.24876@mm:

    • Aware of Eudora address books (listed in Eudora.ini).
    • Deletes *.ntz while searching for files.
    • Attempts to disable the user interface of ZoneAlarm (This does not disable the ZoneAlarm firewall functionality.).
    • Adds an entry to the Shell=explorer.exe line in the Boot section of System.ini, calling the W32.Magistr.Trojan. In some cases, it may add one or more registry entries.
    • Searches for more Windows folders (Winnt, Windows, Win95, Win98, Winme, Win2000, Win2k, Winxp).
    • Emails an attachment that has a random extension (.exe, .bat, .pif, or .com).
    • Occasionally attaches .gifs to emails.
    • The payload overwrites the files, Ntldr (Windows NT/2000/XP) and Win.com (all the Windows 32 OSs), on all the drives with code that causes it to store garbage data in the first sector of the first IDE hard drive.


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.


Removal using the W32.Femot.Worm Removal Tool
Symantec Security Response has created a tool to remove W32.Magistr.39921@mm, which is the easiest way to remove this threat.

Manual removal
Use this procedure if you cannot obtain the removal tool.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan and delete all the files detected as W32.Magistr.39921@mm.
  4. Edit the registry.
  5. For Windows 95/98/me: Remove the W32.Magistr.Trojan entry in the Shell= line of the System.ini file.
For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder ," Article ID: Q263455.

2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Scanning for and deleting the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan. If any files are detected as infected by W32.Magistr.39921@mm, write down the file names, and then click Repair. Delete the files that cannot be repaired. If necessary, restore any deleted files from a clean backup.

    WARNING: Restore the files that are detected as W32.Magistr.Trojan (note the Trojan extension) from backup copies, or extract them from the original installation CD. These files are the system files, Ntldr and Win.com.

    Ntldr is found on Windows NT/2000/XP computers. Win.com is found on all the Windows 32-bit operating systems.

    Do not skip this step. Your system will not properly function without them. For information on how to do this, refer to your Windows documentation, or to one of the following documents:

4. Editing the registry

CAUTION : We strongly recommend that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to back up the Windows registry ," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type regedit, and then click OK. (The Registry Editor opens.)
  3. Navigate to the following key:


  4. In the right pane, look for a value that has a random file name with the .exe extension, and that points to the \WinNT\System or \Windows\System folder. This may be the file name that was detected as W32.Magistr.39921@mm when you ran the full system scan.

  5. Delete any such values that you find.
  6. Do one of the following:
    • If you are running Windows 95/98/Me, click Registry, and then click Exit.
    • If you are running Windows NT/2000/XP, proceed to step g.

  7. Navigate to the following key:


  8. In the right pane, double-click the value: Shell

  9. Look in the value data box, which should contain the text Explorer.exe only, as shown:

  10. If it contains any text to the right of Explorer.exe, for example, warm.exe,

    remove that text so that only Explorer.exe remains, as shown in step 9.

  11. Click Registry, and then click Exit.

5. For Windows 95/98/me: Removing the W32.Magistr.Trojan entry from System.ini
  1. Click Start, and then click Run.
  2. Type the following:

    edit c:\windows\system.ini

    and then click OK. (The MS-DOS Editor opens.)

    NOTE: If Windows is installed in a different location, make the appropriate path substitution.

  3. In the [boot] section of the file, look for the following entry:


  4. Position the cursor immediately to the right of Explorer.exe.
  5. Press Shift+End to select all the text to the right of Explorer.exe, and then press Delete.
  6. Click File, and then click Exit.
  7. Click Yes when you are prompted to save the changes.

NOTE: If you still have problems after following these removal instructions, follow the instructions in the Removal section of W32.Magistr.24876@mm .

Writeup By: Peter Ferrie