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Discovered: April 04, 2003
Updated: February 13, 2007 11:45:23 AM
Type: Worm
Systems Affected: Windows

W32.HLLW.Gaobot.P is a worm that attempts to spread itself to the network shares. This threat also allows for a hacker to remotely access an infected computer through IRC.

W32.HLLW.Gaobot.P is compressed with UPX.

Antivirus Protection Dates

  • Initial Rapid Release version April 04, 2003
  • Latest Rapid Release version August 20, 2008 revision 017
  • Initial Daily Certified version April 04, 2003
  • Latest Daily Certified version August 20, 2008 revision 016
  • Initial Weekly Certified release date April 09, 2003

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

Writeup By: Yana Liu

Discovered: April 04, 2003
Updated: February 13, 2007 11:45:23 AM
Type: Worm
Systems Affected: Windows

When W32.HLLW.Gaobot.P runs, it does the following:

  1. Copies itself as:
    • %System%\Svchosl.exe
    • %System%\Winhlpp32.exe

      NOTE: %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Adds the string value:

    "Config Loader"="svchosl.exe"

    to these registry keys:


    so that the worm runs when you start Windows.
  3. Creates the registry keys:


    and adds this string value to the keys:

  4. Creates the registry keys:


    and adds this string value to the key:

  5. Drops the file, %System%\Psexec.exe, which is 122,880 bytes in length. This is the Sysinternals remote execution utility.
  6. Adds itself as a service with the name, "PSINFSVC" or "PsInfo Servic."
  7. Opens a randomly changed TCP port to connect to the hacker.
  8. Contains its own IRC client, allowing it to connect to an IRC channel that the worm predefines. Using the IRC channel, the worm listens for the commands from the hacker, who may perform any of the following actions:
    • Manages the installation of the worm
    • Dynamically updates the installed worm
    • Downloads and executes the files, which the hacker selects
    • Steals the compromised system information
    • Steals the CD-keys of some electronic games
    • Sends the worm to other IRC users
    • Launches flooding attacks
    • Opens/Closes the CD-ROM drive
    • Scans for and attempts to log in to the Microsoft SQL Servers

  9. Probes the IPC$ shares using trivial user/password combinations. The worm uses Psexec.exe to copy itself as %Windir%\System32\Winhlpp32.exe to the shares and executes this copy in the remote computers. This action will only succeed if an open IPC$ exists.

    NOTE: %Windir% is a variable. The worm locates the Windows installation folder of the remote system and copies itself to the folder system32 under this location. By default, %Windir% is C:\Windows or C:\Winnt.
  10. Creates a named Pipe \\.\pipe\psexecsvc and redirects the information from the pipe to the command psexec.exe.


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: Yana Liu

Discovered: April 04, 2003
Updated: February 13, 2007 11:45:23 AM
Type: Worm
Systems Affected: Windows

The following 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.Gaobot.P.
  3. Restart the computer in Safe mode.
  4. Reverse the changes made to the registry.
For specific details on each of these steps, 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 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. 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.Gaobot.P, click Delete.

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

4. Reversing the changes made to the registry

CAUTION : Symantec strongly recommends backing 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 each of the keys:

  4. In the right pane, delete this value:

    "Config Loader"="svchosl.exe"
  5. Navigate to these keys and delete them:

  6. Exit the Registry Editor.

Writeup By: Yana Liu