Class Email-Worm
Platform VBS

Technical Details

Type: Email Worm
Platform: MS Windows with Internet Explorer 5.0,
MS Outlook 98/2000 or MS Outlook Express

This is an Internet virus-worm that spreads via the Internet as infected e-mail messages.
The worm arrives as a message with no attachment, and the worm uses several tricks
to activate its code directly from the message body. When this message is
opened, the worm code takes control, gains access to system resources (disk
files and system registry), processes the Outlook address book, and sends
infected messages to these addresses (in a similar way that the
Macro.Word97.Melissa virus does).

This is the first known modern Internet worm that spreads its copies with
no attached data. As is the case with other Internet worms, a user must open the
attachment in order to activate the worm’s routines, which take control at the moment the message itself is opened.

The Deceptions

To spread its copies, this worm uses two means of deception. The first one is the
MS Outlook feature allowing the creation of messages in HTML format.
HTML messages may contain scripts that will be automatically executed at
the moment the HTML message is being displayed (user opens the message).
The worm uses this feature to run its code when the infected message is

To spread its copies further and to bypass Internet Explorer security, the
worm uses another trick. At the moment, this is termed the
“Scriptlet.Typelib” security vulnerability.

This security breach allows HTML scripts to create disk files. The worm uses
this breach to create a HTA-file (HTML Applications, new type appeared with
IE5), which contains the main worm code. This file is created in the Startup
Windows folder, and as a result, it is activated upon the next Windows startup.
Being run as a local disk file, the worm’s script in this HTML gains access to
disk files and resources without any Internet Explorer security warning
messages, connects to the Outlook address book, and spreads itself.

Technical details

When a user opens an infected message, the worm script embedded into this
message body is automatically activated and executed by MS Outlook. This
script (by using security breach) creates the “UPDATE.HTA” file in the
“C:WINDOWSSTART MENUPROGRAMSSTARTUP” directory. This is the same file the worm
tries to create in the “C:WINDOWSMENU INICIOPROGRAMASINICIO” directory
(Spain Windows default name).

This “UPDATE.HTA” file contains the main worm code. It will be executed upon
the next Windows startup, because of its location in the Startup folder. The
worm has a minor bug here: it assumes that Windows is always installed in
the C:WINDOWS directory. If this is not the case, the worm cannot create its file and
fails to replicate further.

When the UPDATE.HTA file is executed, the worm runs the Outlook application in
a hidden window and creates a new message to all recipients from the Outlook
address book in the same way as the “Melissa” virus does. This new message has
the HTML format and contains the worm’s script in the body. The message subject is
“BubbleBoy back!”, and the text body appears as follows:

 The BubbleBoy incident, pictures and sounds

After this message has been sent, the worm creates the following in the system registry key in order to prevent duplicate messages from being sent:

 "HKEY_LOCAL_MACHINESoftwareOUTLOOK.BubbleBoy" = "OUTLOOK.BubbleBoy 1.0 by Zulu"

At the end, the worm leaves, on the screen, a window with the following text inside:

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

The worm also changes the Windows registration data (this routine is
executed at the moment the UPDATE.HTA script takes control):

  RegisteredOwner = "BubbleBoy"
  RegisteredOrganization = "Vandelay Industries"


Microsoft has released an update that eliminates security the “Scriptlet.Typelib”
vulnerability. We strongly recommend you visit
and install this update.

If you do not use any HTML applications (HTA-files), there is
another way to prevent infection by viruses of this type (the worms and
viruses that use the “Scriptlet.Typelib” security vulnerability). It is necessary to remove the file association for the .HTA extension. To do this, you have to follow
several steps:

  1. Double click the “My Computer” icon on the desktop.
  2. In the open window, choose menu “View” -> “Options…”.
  3. On the “File Types” tab in the “Registered file types” listbox, select the “HTML Applicaton” item.
  4. Click the “Remove” button and confirm action.
  5. Close options dialogue box.
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