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Discovered: September 07, 2001
Updated: February 13, 2007 11:37:14 AM
Also Known As: W32.CodeBlue
Type: Worm

At this time, Symantec Security Response has not received any reports of this worm being "in the wild" (actual infections).

W32.BlueCode.Worm is a worm that uses the known IIS Web Directory Traversal exploit. Information and a patch for this exploit are located at http://www.microsoft.com/technet/security/bulletin/ms00-078.asp . Systems that have been patched are not affected.

Antivirus Protection Dates

  • Initial Rapid Release version September 07, 2001
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version September 07, 2001
  • Latest Daily Certified version August 09, 2016 revision 001

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

Writeup By: Eric Chien

Discovered: September 07, 2001
Updated: February 13, 2007 11:37:14 AM
Also Known As: W32.CodeBlue
Type: Worm

The worm infects computers running Windows NT and 2000 by using the Unicode Web Traversal IIS exploit. Information about this exploit is available at http://www.microsoft.com/technet/security/bulletin/ms00-078.asp .

Using the exploit, the worm does the following:

  1. It executes FTP on the victim server to retrieve the file Httpext.dll from the attacking server. Httpext.dll is placed in an executable directory (such as C:\Inetpub\wwwroot\scripts) on the victim server.
  2. Next, the worm executes Httpext.dll on the victim server by making an HTTP GET call to the malicious .dll.

    NOTE: Httpext.dll is an ISAPI .dll. To execute it, the worm accessed it as a URL (for example, http:/ /domain.tld/scripts/httpext.dll).
  3. The .dll creates a mutex named "CodeBlue" so that it will execute only once. Then, the .dll creates the C:\Svchost.exe file and executes it.
  4. Svchost.exe performs the infection and denial-of-service routines:
    1. First, the value

      Domain Manager C:\svchost.exe

      is added to the registry key


      which allows the worm to execute after a restart.
    2. Next, the worm drops a temporary file, C:\d.vbs. This file is a Visual Basic Scripting file and is executed by the virus by calling C:\WINNT\system32\Wscript.exe.
    3. The VBS file removes the .ida, .idq, and .printer IIS service mappings preventing other exploits such as Code Red. The worm later deletes this file.
    4. Next, the worm generates random IP addresses, and the infection routine begins again.
    5. If the time is between 10 A.M. and 11 A.M., the worm attempts a denial-of service-attack by sending a large amount of data to an Internet security company's Web site, which is located in China.
    6. Finally, multiple threads are created which can cause system instability and force the system to be inoperable.


    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: Eric Chien

    Discovered: September 07, 2001
    Updated: February 13, 2007 11:37:14 AM
    Also Known As: W32.CodeBlue
    Type: Worm

    To remove the worm, delete files that are detected as W32.BlueCode.Worm and remove the registry entry that the worm added.

    To remove the worm:

    1. Run LiveUpdate to make sure that you have the most recent virus definitions.
    2. Start Norton AntiVirus (NAV), and run a full system scan. Be sure that NAV is configured to scan all files.
    3. Delete all files that are detected as W32.BlueCode.Worm.

    To edit the registry:

    CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.
    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 and select the following key:

    4. In the right pane, look for and select the value

      Domain Manager
    5. Press Delete, and then click Yes to confirm.
    6. Exit the Registry Editor.

    Writeup By: Eric Chien