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Discovered: February 03, 2003
Updated: February 13, 2007 11:42:42 AM
Also Known As: WORM_WINUR.A [Trend], W32/Winur.worm.a [McAfee], Worm.P2P.Winur [KAV]
Type: Worm
Systems Affected: Windows

W32.HLLW.Winur is a worm that uses the KaZaA and WinMX file-sharing programs to spread itself. This worm can also perform Distributed Denial of Service (DDoS) attacks.

W32.HLLW.Winur is written in Microsoft Visual Basic, version 6.

Antivirus Protection Dates

  • Initial Rapid Release version February 03, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version February 03, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date February 05, 2003

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

Technical Description

When W32.HLLW.Winur is executed, it does the following:

  1. Copies itself as these two files:
    • C:\klez_removal.exe
    • A:\Important - read this.doc <62 spaces> .exe

      NOTE: There are 62 blank spaces between the first extension (.doc) and the second extension (.exe) to make you think that the file is a Microsoft Word document when it is actually an executable file.

  2. Creates the hidden folder, C:\Winrun.

  3. Copies itself to the C:\Winrun folder as the following files:
    • .exe
    • Adobe Photoshop cracker.exe
    • Age of Empire crack.exe
    • Age of Mythology cracker.exe
    • All Microsoft games cracker.exe
    • Anastacia game.exe
    • AOL hacker.exe
    • AOL password stealer.exe
    • Britney spears game.exe
    • Bugbear remover.exe
    • Christina Aguilera game.exe
    • Die another Day DVD full.exe
    • Die another day flash movie(1).exe
    • Die another day flash movie.exe
    • Dvd ripper.exe
    • EA games Keygen.exe
    • Esafe desktop protection crack.exe
    • Frontpage cracker.exe
    • Hotmail account hacker in 30 minutes.exe
    • Hotmail hacker.exe
    • Hotmailhacker v1.0.exe
    • ICQ hacker.exe
    • ICQ password stealer.exe
    • Jack the ripper v1.0.exe
    • Jackie chan dvd collection.exe
    • James Bond game - Die another day.exe
    • John the ripper v1.0.exe
    • Justin Timberlake Debute movie.exe
    • kazaa.exe
    • kazaa.url.exe
    • Klez fixtool.exe
    • Lord of the rings VCD.exe
    • Love calculator.exe
    • Mcafee virusscanner crack.exe
    • Microangelo cracker.exe
    • Most important hacker tool ever!.exe
    • msconfig.exe
    • MSN Messenger commercial cracker.exe
    • MSN Password stealer.exe
    • MXlinx 0.30 crack.exe
    • Nikki cox game and movie.exe
    • Norton antivirus cracker.exe
    • Office XP license cracker.exe
    • pornmovie (hardcore sex adult asian).exe
    • Red Alert cracker - All versions.exe
    • Rollercoaster tycoon cracker.exe
    • Shriek DVD crack patch.exe
    • Stop the war (intro).exe
    • Super 2000key keygen.exe
    • Theme park world cracker.exe
    • UnIcOrn Gift.exe
    • Warcraft 3 cracker.exe
    • Website hacker v1.0.exe
    • Windows Me crack.exe
    • Windows XP license cracker.exe
    • Yaha Fixtool.exe

  4. Adds the value:

    msconfig C:\winrun\msconfig.exe

    to the registry key:


    so that the worm runs when you start Windows.

  5. Adds the value:

    winrun c:\winrun\msconfig.exe

    to the registry key:


    so that the worm runs when you start Windows.

  6. Adds the value:

    "IMWarning"="(M)Warning: The person who you are talking to is infected with a virus. Send him the removal tool that can be found in C:\klez_removal.exe(M)"

    to the registry key:


    This generates a warning message in MSN Messenger encouraging the user, with the infected system, to send a copy of the worm to his/her contacts.

  7. Decreases the security level of the KaZaA file-sharing software (if you have the software installed), by adding or modifying the following values:
    • ScanFolder 0x00000001

      in these registry keys:

    • IgnoreAll 0x00000001

      in these registry keys:

    • AutoConnected 0x00000001

      in these registry keys:

    • FolderWarning 0x00000000

      in these registry keys:

    • The following values:

      dir0 13263:C:\Winrun
      DisableSharing 0x00000000

      in these registry keys:

    • The following values:

      adult_filter_level 0x00000000
      bogus_filter 0x00000000
      fiwewall_fileter 0x00000000
      virus_filter 0x00000000

      in these registry keys:

    • Quarantine %Windows%\%StartupPath%

      in these registry keys:


  8. Creates the following files:
    • C:\Autostart.bat
    • C:\Ntwrk32.dll

      NOTE: These files are not malicious, and thus Symantec antivirus products do not detect them as such. You should manually delete them if found.

  9. Attempts to perform a DDoS attack on three specific Web sites.


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.


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

  1. Update the virus definitions.
  2. Run a full system scan and delete all the files detected as W32.HLLW.Winur. Manually delete C:\Autostart.bat and C:\Ntwrk32.dll if they exist.
  3. Reverse the changes that the worm made to the registry.
For specific details on each of these procedures, read the following instructions.

1. 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.

2. 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 infected with W32.HLLW.Winur, click Delete.
  4. Using Windows Explorer, look for the files, C:\Autostart.bat and C:\Ntwrk32.dll. Delete them if found.

3. Reversing the changes made to the registry

CAUTION : 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, and then click OK. (The Registry Editor opens.)
  3. Navigate to the key:


  4. In the right pane, delete the value:

    msconfig C:\winrun\msconfig.exe

  5. Navigate to the key:


  6. In the right pane, delete the value:

    winrun c:\winrun\msconfig.exe

  7. Navigate to the key:


  8. In the right pane, delete the value:

    "IMWarning"="(M)Warning: The person who you are talking to is infected with a virus. Send him the removal tool that can be found in C:\klez_removal.exe(M)"

  9. If you have KaZaA installed, restore the security settings that you normally use. See step 7 in the "Technical Details" section for a list of modified keys.
    (You may be able to restore many of these settings within the KaZaA program. Refer to your KaZaA documentation for additional information, or contact KaZaA technical support.)

  10. Exit the Registry Editor.

Writeup By: Kaoru Hayashi