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09 November 1999
13 February 2007
Also Known As:
VBS/BubbleBoy@MM [McAfee], I-Worm.BubbleBoy [AVP], VBS_BUBBLEBOY [Trend], VBS/BubbleBoy.Worm [CA], VBS/BubbleBoy [Panda], VBS/BubbleBoy-A [Sophos]
Systems Affected:
CVE References:

VBS.BubbleBoy is a worm that works under Windows 98 and Windows 2000. The worm also works under Windows 95, but only if the Windows Scripting Host is installed. The worm only works with the English and Spanish versions of these operating systems, and does not work under Windows NT.

The computer must use Microsoft Outlook (or Express) with Internet Explorer 5 in order for the worm to propagate.

The worm utilizes a known security hole in Microsoft Outlook/IE5 to insert a script file, Update.hta, when the email is viewed. It is not necessary to detach and run an attachment.

Update.hta is placed in the StartUp folder. Therefore, the infection routine is not executed until the next time you start your computer. Update.hta is a script file that uses MS Outlook to send the worm email message to everyone in the MS Outlook address book.

Patching the known security hole in Microsoft Outlook/IE5, prevents the worm from propagating. For further information regarding the security hole, please read the following Microsoft article:

Microsoft has provided a patch to fix this problem at

The worm will not propagate if IE5 Internet security settings have been set to "High."

Antivirus Protection Dates

  • Initial Rapid Release version 15 November 1999
  • Latest Rapid Release version 08 August 2016 revision 023
  • Initial Daily Certified version 15 November 1999
  • Latest Daily Certified version 09 August 2016 revision 001
  • Initial Weekly Certified release date 15 November 1999
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

If the security hole has not been patched, VBS.BubbleBoy inserts the Update.hta file as soon as the email is opened. The email contains the text

Subject: BubbleBoy is back!
    The message body contains the text

    The BubbleBoy incident, pictures and sounds
    http:/ /
      This is how the message appears:

      The body of the message is created with HTML using VBScript, which is not normally visible. The VBScript is executed without prompting the user (due to the security hole). The script creates and inserts a file named Update.hta into C:\Windows\Start Menu\Programs\StartUp or C:\Windows\Menú Inicio\Programas\Inicio.

      If neither of these directories exists, the worm fails. Update.hta also contains VBScript, which performs the mass-mailing routine. There is no attachment to the message; the worm is fully contained within the nonvisible VBScript inside of the message body. The worm automatically executes the next time Windows starts and performs the following steps:
      1. The worm changes the registered owner to BubbleBoy by modifying the following registry key:

      2. The worm changes the registered organization to Vandelay Industries by modifying the following registry key:

      3. The worm checks to see whether the registry key


        has been set to

        OUTLOOK.BubbleBoy 1.0 by Zulu

        If the registry has already been set, then the worm will not continue to perform its infection routine. This causes the worm to perform its mass mailing routine only once.
      4. Using MAPI, the worm composes an email message to everyone in the MS Outlook address book. The subject and body of the message are described above. No record of the sent messages appears in MS Outlook.
      5. Next, the worm sets the registry key

        HKEY_LOCAL_MACHINE\Software\OUTLOOK.BubbleBoy\ =OUTLOOK.Bubbleboy 1.0 by Zulu

        to mark the execution of its worm routine.
      6. Finally, the worm displays a window with the following text:

        System error, delete "UPDATE.HTA" from the startup folder to solve this problem

      Variant notes

      The B variant (also detected as VBS.BubbleBoy) is encrypted. The registry entry to mark the worm routine execution is

      HKEY_LOCAL_MACHINE\Software\OUTLOOK.BubbleBoy\ =OUTLOOK.Bubbleboy 1.1 by Zulu


      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.

      To remove this worm:
      1. Delete the following files:

        C:\Windows\Start Menu\Programs\StartUp\Update.hta
        C:\Windows\Menú Inicio\Programas\Inicio\Update.
      2. Restore the following registry keys to their proper values:

      3. Remove the following registry key:


        NOTE: Not removing this key will actually prevent the worm from propagating again.
      Prevention Information

      Microsoft has provided a patch to prevent the worm from propagating by viewing an infected email in Outlook. Security Response recommends downloading this patch from the following Web site:

      Also, Symantec Security Response recommends monitoring the following Web site for any Microsoft security updates:

      Writeup By: Eric Chien