Printer Friendly Page

Discovered: November 06, 2003
Updated: February 13, 2007 12:13:26 PM
Also Known As: Bloodhound.W32.VBWORM, W32/Wukill.worm [McAfee]
Type: Worm
Systems Affected: Windows

W32.Wullik.B@mm is a mass-mailing worm that attempts to send itself to all the contacts in the Outlook address book.

The email has the following characteristics:

Subject: MS?DOS???? (the ?'s represent Chinese characters.)
Attachment: MShelp.EXE
Message: <Chinese text>

The worm makes numerous copies of itself in random locations, and moves to a new location when Windows Explorer browses to the folder from which it runs. It can spread to floppy disks and shared network drives under some conditions.

W32.Wullik.B@mm is written in Visual Basic. Virus definitions dated prior to November 7, 2003 may detect it as Bloodhound.W32.VBWORM.

Antivirus Protection Dates

  • Initial Rapid Release version November 07, 2003
  • Latest Rapid Release version May 07, 2019 revision 006
  • Initial Daily Certified version November 07, 2003
  • Latest Daily Certified version May 07, 2019 revision 008
  • Initial Weekly Certified release date November 12, 2003

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

Technical Description

When W32.Wullik.B@mm is executed, it does the following:

  1. Copies itself to the following locations:
    • %Windir%\Mstray.exe
    • %Windir%\MShelp.EXE

      Note: The worm uses this icon to disguise itself as a folder, rather than an executable file:

      Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

  2. Monitors active windows. When a window moves to the foreground, the worm may create new copies of itself, depending on the content of the title bar.

    If the title bar matches the current location of the worm:
    The worm creates a new copy of itself in a random location, launches the new copy, and then exits. The new copy of the worm then deletes the old.

    For example, if the worm is running as C:\Windows\Mstray.exe, and you browse to C:\Windows using Windows Explorer, the title bar is "C:\Windows." The worm may then copy itself to C:\Windows\Temp\xyz.exe. Xyz.exe deletes Mstray.exe.

    If the title bar is any other path:
    The worm copies itself to a file that matches the name of the directory. This file has the hidden attribute.

    For example, if you use Windows Explorer to browse to C:\Windows\Mydir, the worm copies itself as C:\Windows\Mydir\Mydir.exe.

    Note: This functionality could be used to spread across network shares.

    If the title bar is anything else:
    The worm may create files of the form:
    • ***WINFILE.EXE: another copy of the worm
    • ***comment.htt: A hypertext template file, detected as JS.Exception.Exploit. This file is used to launch winfile.exe on systems that are vulnerable to this exploit.
    • ***desktop.ini
      where *** matches the first three characters of the title bar.

  3. Adds the values:

    "RavTimeXP"= <the current filename used by the worm>
    "RavTimXP"= <the last filename used by the worm>

    to the registry key:


    so that the worm runs when you start Windows.

  4. Adds the value:


    to the registry key:


    This appears to be used to store internal configuration information for the worm.

  5. Sets the value:

    "fullpath" = 0x1

    in the registry key:


    This ensures that the full path appears in the title bar of Windows Explorer.

  6. Sets the values:

    "HideFileExt" = 0x1
    "Hidden" = 0x0

    in the registry key:


    This prevents Explorer from displaying file extensions and hidden files.

  7. May email itself to all the contacts in the Outlook address book.

    The email has the following form:

    Subject: MS?DOS???? (where the ?'s represent Chinese characters.)
    Attachment: MShelp.EXE
    Message: <Chinese text>


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.


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Wullik.B@mm or JS.Exception.Exploit. Delete the desktop.ini files that the worm created.
  5. Remove the registry entries that the worm added.
  6. Optional: Restore the Windows Explorer settings to your preferred configuration.
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. Restarting the computer in Safe mode or VGA mode

Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
  • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
  • For Windows NT 4 users, restart the computer in VGA mode.

4. 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.
  3. If any files are detected as W32.Wullik.B@mm or JS.Exception.Exploit, note the path and file name, and then click Delete.
  4. For each file detected as JS.Exception.Exploit, delete the corresponding desktop.ini file. For example, if "ABCcomment.htt" was detected as JS.Exception.Exploit, delete "ABCdesktop.ini" from the same directory.

5. Removing the value from the registry

WARNING: Symantec strongly recommends 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 make a backup of the Windows registry ," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to the key:


  4. In the right pane, delete these values:


  5. Navigate to the key:


  6. In the right pane, delete this value, if found:


  7. Exit the Registry Editor.

6. Optional: Configuring Windows Explorer
  1. Double-click "My Computer."
  2. Select "Tools" or "View" (depending on the operating system).
  3. Select the menu item "Folder Options."
  4. Click on the tab labeled "View."
  5. Adjust the settings that the worm modified:

    "Display the full path in title bar"
    "Do not show hidden or system files"
    "Hide file extensions for known file types"

    (The exact wording may vary, depending on the operating system.)

Writeup By: Heather Shannon