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Discovered: August 10, 2001
Updated: February 13, 2007 11:58:33 AM
Type: Worm

W32.HLLW.Hai is a worm written in C++. This worm spreads its infection in a manner that is very similar to worms such as W32.HLLW.Bymer and W32.HLLW.Qaz . It spreads by finding computers that share the \Windows folder with full access set to "Everyone." If such a share is found, the worm copies itself to the share and modifies the Win.ini file so that the worm is executed when the computer is restarted. This worm cannot spread to computers that do not have the NetBIOS protocol installed.

It is never a good idea to share the entire hard drive or the \Windows folder with full access for "Everyone." By having a share like this, anyone on the Internet who knows your IP address will have full access to any files within that share. If you need to have shares on your computer, it is highly recommended that you protect them with a password. For more information on configuring shares please see the Knowledge Base article, How to configure shared Windows folders for maximum network protection .

What are Portable Executable (PE) files?
PE files are files that are portable across all Microsoft 32-bit operating systems. You can execute the same PE-formatted file on any version of Windows 95, 98, Me, NT, and 2000. Therefore, all PE files are executable, but not all executable files are portable.

A good example of a Portable Executable is a screen saver (.scr) file.

Antivirus Protection Dates

  • Initial Rapid Release version August 10, 2001
  • Latest Rapid Release version March 03, 2008 revision 035
  • Initial Daily Certified version August 10, 2001
  • Latest Daily Certified version March 03, 2008 revision 037

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

Writeup By: Neal Hindocha

Discovered: August 10, 2001
Updated: February 13, 2007 11:58:33 AM
Type: Worm

W32.HLLW.Hai is a worm that spreads over a network. It spreads by looking for computers 1) on which the NetBIOS protocol is installed, and 2) that share the \Windows folder with full access for "Everyone." The worm does this by spawning a new thread that looks for computers with open Windows shares. When it finds such a computer, the worm copies itself into the \Windows folder. It also modifies the Win.ini file so that the next time the computer is started, the worm will be executed.

The file name that this worm uses is chosen at random, for example, C:\Windows\Iegup.exe, Jkvjhb.exe. or Pueqfwh.exe.

All of the samples of this worm that Symantec Security Response has received have been encrypted with a known Portable Executable (PE) file-encryption program.


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: Neal Hindocha

Discovered: August 10, 2001
Updated: February 13, 2007 11:58:33 AM
Type: Worm

Run LiveUpdate to make sure that you have the most recent virus definitions.

  1. Start Norton AntiVirus (NAV), and run a full system scan. Be sure that NAV is configured to scan all files.
  2. Delete all files that are detected as W32.HLLW.Hai.
  3. Click Start, and click Run.
  4. Type the following, and then click OK.

    edit c:\windows\win.ini

    The MS-DOS Editor opens.

    NOTE: If Windows is installed in a different location, make the appropriate path substitution.
  5. In the [windows] section of the file, look for the line that begins with

  6. If the line exists, and if there is text to the right of the = sign, examine the text carefully. If you are not absolutely sure that the text refers to a program that you are familiar with, and that you want to run when the computer starts, delete the text.
  7. Click File, and then click Exit. Click Yes when prompted to save changes.

Writeup By: Neal Hindocha