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Discovered: June 18, 2002
Updated: February 13, 2007 11:48:24 AM
Also Known As: W32/Kwbot.worm [McAfee], W32/KWBot-A [Sophos], Win32.Kowbot.12 [CA], WORM_KWBOT.A [Trend], Worm.Win32.SdBot [AVP]
Type: Worm
Systems Affected: Windows

W32.Kwbot.Worm has backdoor Trojan capability, which allows a hacker to gain control of the compromised computer. The worm can update itself by checking for newer versions over the Internet. W32.Kwbot.Worm disguises itself as popular movie, game, or software files, and it attempts to spread across KaZaA file-sharing networks by tricking KaZaA users into downloading the program and opening it.

November 6, 2002. Changed to Category 2 based on increased prevalance.

Antivirus Protection Dates

  • Initial Rapid Release version June 19, 2002
  • Latest Rapid Release version November 04, 2019 revision 019
  • Initial Daily Certified version June 19, 2002
  • Latest Daily Certified version November 04, 2019 revision 065
  • Initial Weekly Certified release date June 19, 2002

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

Technical Description

When W32.Kwbot.Worm runs, it does the following:

It copies itself as C:\%System%\Explorer32.exe.

NOTE : %System% is a variable. The worm locates the \Windows\System folder (by default this is C:\Windows\System or C:\Winnt\System32) and copies itself to that location.

It adds the value

Windows Explorer Update Build 1142  C:\%SYSTEM%\EXPLORER32.EXE

to the following registry keys:


This causes the worm to run when you start Windows.

The worm opens a randomly chosen TCP port to connect to the hacker.

W32.Kwbot.Worm contains its own Internet Relay Chat (IRC) client. This allows the worm to connect to an IRC channel that was coded into the Trojan. Using the IRC channel, the Trojan listens for commands from the hacker. The hacker accesses the Trojan by using a password-protected authorization. The commands allow the hacker to perform any of the following actions:

  • Manage the installation of the backdoor
  • Control the IRC client on the compromised computer
  • Dynamically update the installed Trojan
  • Send the Trojan to other IRC channels to attempt to compromise more computers
  • Download and execute files
  • Deliver system and network information to the hacker
  • Perform Denial of Service (DoS) attacks against a target that is defined by the hacker
  • Uninstall itself completely by removing the relevant registry entries

How it spreads

NOTE: For W32.Kwbot.Worm to spread, it requires that the KaZaA software be installed on the computer.

The worm searches the Windows registry to locate the KaZaA shared folder. Other KaZaA users can download files from that location. The worm then copies itself into this folder using many different names that are chosen randomly from a list that the worm carries. Here are some examples:
  • Sum of all Fears SVCD CD3.exe
  • Star Wars Episode 2 - Attack of the Clones VCD CD2.exe
  • Spiderman SVCD CD3.exe
  • Grand Theft Auto 3 CD2 ISO.exe
  • Playstation 2 PS2 Emulator.exe
  • Windows XP Home to Professional Upgrade.exe
  • Windows XP backdoor hack.exe
  • Windows 2000 win2k password stealer.exe
  • Microsoft Office XP Upgrade (from older versions).exe
  • Macromedia Flash 5 Ultimate Study Guide.exe
  • ZoneAlarm Firewall Pro.exe
  • Norton Internet Security 2002.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.


Update the virus definitions, restart in Safe mode, and run a full system scan. Delete all files that Norton AntiVirus detects as W32.Kwbot.Worm.

  1. Delete the value

    Windows Explorer Update Build 1142

    from the following registry keys:


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

To scan with Norton AntiVirus and delete the infected files:
  1. Obtain the most recent virus definitions. There are two ways to do this:
    • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time 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 have undergone full quality assurance testing by Symantec Security Response. They 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.
  2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
  3. Run a full system scan.
  4. Delete all files that NAV detects as W32.Kwbot.Worm.

To remove the value 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 only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to each of these keys:


    For each one, look in the right pane, and delete this value:

    Windows Explorer Update Build 1142
  4. Click Registry, and click Exit.

Writeup By: Yana Liu