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Discovered: February 12, 2003
Updated: February 13, 2007 11:43:02 AM
Also Known As: W32/Gool.worm [McAfee], W32/Igloo-15 [Sophos], WORM_GOOL.A [Trend]
Type: Worm
Systems Affected: Windows

W32.HLLW.Gool attempts to spread across the KaZaA file-sharing network and through IRC.

W32.HLLW.Gool has backdoor Trojan capabilities that allow a hacker to gain control of the compromised computer. The TCP port that the worm uses to connect to the hacker is 31,337 by default. The port number can be configured by using the server editor component.

This worm attempts to terminate some popular antivirus and security products processes if they are running.

W32.HLLW.Gool is written in the Borland Delphi programming language.

Antivirus Protection Dates

  • Initial Rapid Release version February 13, 2003
  • Latest Rapid Release version May 07, 2019 revision 006
  • Initial Daily Certified version February 13, 2003
  • Latest Daily Certified version May 07, 2019 revision 008
  • Initial Weekly Certified release date February 19, 2003

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

Technical Description

W32.HLLW.Gool has three components:

  • Server. This is the component that runs on and compromised a computer.
  • Server editor. The server editor allows the hacker to configure the TCP port and the ICQ page number for the notification that is sent to the hacker.
  • Client. The client component is used by the hacker to connect to a compromised computer and take control of it.

When the W32.HLLW.Gool server component runs, it does the following:
  1. Copies itself as:
    • C:\Windows\System\Explorer.exe
    • C:\Windows\System\RealWayToHack.exe
  2. Adds the value:


    to the registry key:


    so that the worm runs when you start Windows.
  3. Changes the Value data of the value RegisteredOrganization in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main


    http:/ /www.crash.com
  4. Attempts to end the processes of several antivirus and security products. The worm inventories the active processes, and if the name of the process is in the list that carried by the worm, it attempts to end the process. Here are some examples:
    • _avp32.exe
    • Navdx.exe
    • Netstat.exe
    • Pcscan.exe
    • Rescue.exe
    • Routemon.exe
    • Safeweb.exe
    • Symproxysvc.exe
    • Tracert.exe
    • Vettray.exe
    • Vsmon.exe
    • Webtrap.exe
    • Zonealarm.exe
  5. Creates the file C:\Windows\System\Explorer.vbs which is 7,425 bytes in length. The worm uses this Visual Basic Script to send a copy of itself to other mIRC users that connect at the same channel as the compromised computer.
  6. Creates the folder C:\Windows\Sys32. It then changes the KaZaA download folder settings in the registry so that this new folder is accessible to other KaZaA network users. This allows other KaZaA users to download files from that location.
  7. Copies itself to the Sys32 folder using many different names that are carried by the worm. Here are some examples:
    • Britney.jpg.exe
    • Divx_repair.jpg.exe
    • Host_faker.jpg.exe
    • Hotmail_account_sniffer.jpg.exe
    • Iis_shellbind_exploit.jpg.exe
    • Ip_spoofer.jpg.exe
    • Linux_root.jpg.exe
    • Porn_account_hacker.jpg.exe
    • Tripod_hacker.jpg.exe
    • Winxp_cracker.jpg.exe
    • Xbox_emulator_beta.jpg.exe
  8. Opens an HTTP connection to a Web server that was chosen by the hacker and posts the compromised computer's IP address and the connection TCP port number to a script file at that Web server. It may also email the hacker the victim's system information.
  9. Opens a TCP port to connect to the hacker. This allows the hacker to take control of the compromised computer. The hacker may perform any of the following actions:
    • Manage the installation of the worm
    • Steal information from the compromised system
    • Delete or execute files of the hacker's choice
    • Log keystrokes
    • Enable or disable Internet Relay Chat (IRC)
    • Annoying actions, such as: Change various desktop settings (wallpaper, icons, screen saver, etc.), reverse the mouse buttons, manipulate the keyboard, open and close the CD-ROM drive, and so on.


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. Restart the computer in Safe mode.
  3. Run a full system scan and delete all the files detected as W32.HLLW.Gool.
  4. Reverse the changes that were 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 the 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), in the "Protection" section, at the top of this writeup.
  • 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), in the "Protection" section, at the top of this writeup.

    The Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

2. Restarting the computer in Safe mode
All the Windows 32-bit operating systems, except Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document, "How to start the computer in Safe Mode ."

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.
  3. If any files are detected as infected with W32.HLLW.Gool, click Delete.

4. Deleting the value from the registry

CAUTION : Symantec strongly recommends that you back up the registry before you make 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 the value:

  5. Navigate to the key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
  6. In the right pane, double-click:


    Replace the text in the Value data box with the name of your organization. (You can just delete the text and leave it blank if desired).
  7. Navigate to the key:

  8. In the right pane, delete the values:

    dir0 012345:C:\Windows\Sys32
    dir1 012345:C:\Windows\Sys32
    dir2 012345:C:\Windows\Sys32
    dir3 012345:C:\Windows\Sys32
    dir4 012345:C:\Windows\Sys32
    dir5 012345:C:\Windows\Sys32
  9. Exit the Registry Editor.

Writeup By: Yana Liu