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Discovered: July 28, 2003
Updated: February 13, 2007 12:03:07 PM
Type: Worm
Systems Affected: Windows

W32.Tzet.Worm is a worm that spreads by attacking computers that have weak administrator passwords or weak default accounts passwords (such as guest). This worm contains a backdoor and allows a remote attacker to re-route their network traffic through an infected host.

Antivirus Protection Dates

  • Initial Rapid Release version July 29, 2003
  • Latest Rapid Release version June 12, 2018 revision 016
  • Initial Daily Certified version July 29, 2003
  • Latest Daily Certified version June 12, 2018 revision 021
  • Initial Weekly Certified release date July 30, 2003

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

Writeup By: Atli Gudmundsson

Discovered: July 28, 2003
Updated: February 13, 2007 12:03:07 PM
Type: Worm
Systems Affected: Windows

When W32.Tzet.Worm is executed, it does the following:

  1. Inserts the following files in the System% folder:
    • Authexec.bat
    • Iglmtray.exe
    • Iglxtray.exe
    • Lrss.ini
    • Mdde32.exe
    • Net.bat
    • Nna.exe
    • Printf_core.exe
    • Vidriv.exe
    • Wmpt.exe
    • Wsubsys.wav
    • Xcopy.dll

      NOTE: Other file names are possible.

  2. Creates the value:


    under the registry key:


  3. Attempts to infect a random system on the Internet (attacking weak administrator or default account passwords), by using a batch file and a utility from Sysinternals, which W32.Tzet.Worm uses to copy itself to and execute on that system.

    The accounts that are attacked are:


    The passwords that it attempts to use include, among others:

    <no password>
    <account name>

    Note: Due to the way the worm attacks remote computers, the spreading cababilities of this worm will not work against or on Windows 95/98/Me systems.

  4. Logs into IRC and announces its presence to the creator(s) of the worm. The IRC connection is attempted on the following servers:


    Once a connection is established, the worm will log into an IRC channel, where the attacker can now remotely control it. The current version logs by default into the channel #º-scan-º# with the password !(sc4n)!.

Additional functionality includes:
  • Remote control (backdoor capability)
  • Re-routing HTTP network traffic through the host computer
  • Stealing key information of various popular games
  • Launching a Denial of Service (DoS) attack against a single computer


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: Atli Gudmundsson

Discovered: July 28, 2003
Updated: February 13, 2007 12:03:07 PM
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. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Do one of the following:
    • Windows 95/98/Me/2000/XP: Restart the computer in Safe mode.
    • Windows NT: End the Trojan process.
  4. Reverse the changes that the Trojan made to the registry.
  5. Run a full system scan and delete all the files detected as W32.Tzet.Worm.
For details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder ," Article ID: Q263455.

2. 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.

3. Restarting the computer in Safe mode or ending the Trojan process
    Windows 95/98/Me
    Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for 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."

    Windows NT/2000/XP
    To end the Trojan process:
    1. Press Ctrl+Alt+Delete once.
    2. Click Task Manager.
    3. Click the Processes tab.
    4. Double-click the Image Name column header to alphabetically sort the processes.
    5. Scroll through the list and look for any of the filenames listed in step 1 of the "Technical Details" section.
    6. If you find the file, click it, and then click End Process.
    7. Exit the Task Manager.

4. Reversing the changes made to the registry

: 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

    Then click OK. (The Registry Editor opens.)

  3. Navigate to the key:


  4. In the right pane, delete the value:


  5. Exit the Registry Editor.
  6. Restart the computer

5. 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.Tzet.Worm, click Delete.

Writeup By: Atli Gudmundsson