Risk Level 2: Low

February 11, 2003
February 13, 2007 11:42:57 AM
Also Known As:
Worm.P2P.Tanked.14 [KAV], Win32/HLLW.Kwbot.C [RAV]
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP


The W32.Kwbot.C.Worm attempts to spread itself through the KaZaA and iMesh file-sharing networks. The worm also has a backdoor Trojan capability that allows a hacker to gain control of a compromised computer.

Antivirus Protection Dates

  • Initial Rapid Release version February 12, 2003
  • Latest Rapid Release version February 3, 2015 revision 032
  • Initial Daily Certified version February 12, 2003
  • Latest Daily Certified version February 3, 2015 revision 034
  • Initial Weekly Certified release date February 12, 2003
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.


When W32.Kwbot.C.Worm runs, it does the following:
  1. Copies itself as one of the following:
    • %System%\System32.exe
    • %System%\Cmd32.exe

      The attribute of this copy is set to Hidden.

      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 one of the following the values:

    SystemSAS system32.exe
    CMD cmd32.exe

    to these registry keys:


    so that the worm runs when you start Windows.

  3. Creates the subkey, krypton, in the registry key:


  4. May change the value data of the value, Shell, in the registry key:

    HKEY_Local_Machine\Software\Microsoft\Windows NT\CurrentVersion\Winlogon


    explorer.exe C:\<The file name of the copy of the worm>

    For example, the value in this registry key may be changed to:

    Shell explorer.exe C:\Windows\system32\cmd32.exe

    In this way, the worm runs when you restart Windows 2000/NT/XP.

  5. Creates one of the following folders:
    • %Windir%\UserTemp
    • %Windir%\User32

  6. Copies itself into the folder that the worm created in the previous step using many different file names that the worm carried. The attributes of all the copies are set to Hidden.

    Some examples of these file names are:
    • Battlefield1942_bloodpatch.exe
    • NBA2003_crack.exe
    • UT2003_keygen.exe
    • Age of Empires 2 crack.exe
    • MediaPlayer Update.exe
    • iMesh 3.7b (beta).exe
    • KaZaA Speedup 3.6.exe
    • Download Accelerator Plus 6.1.exe
    • Network Cable e ADSL Speed 2.0.5.exe
    • Guitar Chords Library 5.5.exe

  7. Adds the value:

    Dir? 012345:%Windir%\UserTemp


    Dir? 012345:%Windir%\User32

    NOTE: "?" in these values represents a number that the worm has chosen.)

    to these registry keys:


    so that other KaZaA or iMesh users may download the files from the %Windir%\UserTemp or %Windir%\User32 folders.

    NOTE: For the worm to spread, it requires the KaZaA or iMesh software be installed on the computer.

  8. Opens two randomly selected TCP and UDP ports to connect to the hacker.

  9. Listens for the commands from the hacker using its own IRC channel. The commands allow the hacker to perform any of the following actions:
    • Upgrade the worm
    • Steal the system and network information from your computer and send it to the hacker
    • Download and execute files
    • Perform Denial of Service (DoS) attacks against a target, which the hacker selects
    • Send the worm to other IRC users


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. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Restart the computer in Safe Mode.
  4. Run a full system scan and delete all the files detected as W32.Kwbot.C.Worm.
  5. Delete the values that the worm added to the registry.

For specific details on each of these procedures, 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:
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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
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. 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.Kwbot.C.Worm, click Delete.
  4. Using Windows Explorer, look for the folders %Windir%\UserTemp and %Windir%\User32, and delete them if they exist.

5. Deleting the values 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 each of the keys:


    NOTE: All of these keys may not be found on all the systems.

  4. From each key, in the right pane, delete these values if you find them:

    SystemSAS system32.exe
    CMD cmd32.exe

  5. Navigate to and delete the key:


  6. Navigate to the key:

    HKEY_Local_Machine\Software\Microsoft\Windows NT\CurrentVersion\Winlogon

    NOTE: This key does not exist on all the systems. If you do not find it, proceed to step i.

  7. In the right pane, double-click: Shell

  8. Change the text in the Value data box so that it reads only:


  9. Navigate to each of the keys:


  10. In the right pane, delete any values that refer to the C:\%Windir%\UserTemp or C:\%Windir%\User32 folders.

    For example:

    Dir? 012345:C:\%Windir%\UserTemp

    NOTE: "?" in this value represents a number that the worm has selected.

  11. Exit the Registry Editor.