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Discovered: December 16, 2002
Updated: February 13, 2007 11:41:35 AM
Also Known As: W32/Lioten.worm [McAfee], Win32.Lioten [CA], WORM_LIOTEN.A [Trend], W32/Lioten-A [Sophos], Worm.Win32.Lioten [KAV]
Type: Worm
Systems Affected: Windows

W32.HLLW.Lioten is a simple worm that attempts to copy itself over Windows NT-based networks. The worm is written in the Visual C programming language and is packed with UPX.

When attempting to find machines to infect, it will query machines on port 445.

By default, installations of Windows NT 4 do not listen on port 445, whereas Windows 2000 and Windows XP installations do listen on port 445.

Antivirus Protection Dates

  • Initial Rapid Release version December 17, 2002
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version December 17, 2002
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date December 18, 2002

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

Technical Description

When W32.HLLW.Lioten runs, it does the following:

It creates 100 threads and starts generating random IP addresses. The randomly generated IP address is one of the following, [0-255].[0-127].[0-255].[0-127]. Therefore, a machine with IP address,, would be immune to this threat due to the second digit being greater than 127. The same is also true if the last digit is greater than 127.

The worm tries to determine if an IP address is valid by querying the IP address on port 445.

Next, it tries to use these valid IP addresses to copy itself to other computers on the network as %system%\Iraq_oil.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).

The worm uses more than 12 different default passwords in its attempt to spread. Among these passwords are: admin, root, 111, 123, 1234, 123456, 654321, 1, !@#$, asdf, asdfgh, !@#$%, !@#$%^, !@#$%^&, !@#$%^&*, and server.

The worm uses the NetScheduleJobAdd function in netapi32 to run the worm at a specified time and date. This function requires that the scheduled service be started on the computer to which the job is submitted. As a result, Windows 95/98/Me systems are not affected because they do not support this functionality.

If there are many infected computers on a network, the worm could cause a Denial of Service because it is running in multiple threads and probing for new IP addresses to infect.


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.


NOTE: These instructions are for 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 files that are detected as W32.HLLW.Lioten.

For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers once each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
  • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

    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.

To scan for and delete the infected files:
  1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.HLLW.Lioten, click Delete.

Writeup By: Jari Kytojoki