Threat Explorer

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20 February 2003
13 February 2007
Also Known As:
VBS.Casechange.A [CA]
Systems Affected:

VBS.Caser@mm is a mass-mailing worm that spreads using Microsoft Outlook and IRC and copies itself across mapped drives. The worm attempts to overwrite several files on your system. The email will have an attachment with a .vbs file extension.

NOTE: Virus definitions dated prior to February 20, 2003 may detect this threat as Bloodhound.VBS.Worm.

Antivirus Protection Dates

  • Initial Rapid Release version 20 February 2003
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 20 February 2003
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 20 February 2003
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When VBS.Caser@mm is executed, it performs the following actions:
  1. Creates a copy of itself as %System%\MSupdt32.vbs.

    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 the value:

    Run MSupdt32 wscript %system%\MSupdt32.vbs %1

    to the registry key:

  3. Creates one or more of the following files, depending on a random value:
    • WUnstc32.vbs
    • WSrvc32.vbs
    • MSinet32.vbs
    • Winlnet.vbs
    • Setupmgr.vbs
    • Instmgr.vbs
    • Ocxmgr32.vbs
    • Cabfldr32.vbs

      The files will be created in either the %System%, %Windir%, or %Temp% folder, depending on a random value.

      • %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and creates the files to that location.
      • %Temp% is a variable that refers to the Windows Temporary folder. The location of this folder can vary.

  4. Overwrites all the .vbs and .vbe files, in the following folders, with a copy of the worm:
    • \Program Files\Limewire\Share
    • \Program Files\Gnucleus\Downloads
    • \Program Files\Gnucleus\Downloads\Incoming
    • \Program Files\Shareaza\Downloads
    • C:\My Documents\My Music
    • C:\My Music
    • C:\MyMusic
    • C:\Kazaa\My Shared Folder
    • C:\My Downloads
    • \Program Files\Kazaa\My Shared Folder
    • \Program Files\Kazaa Lite\My Shared Folder
    • \Program Files\Bearshare\Shared
    • \Program Files\Edonkey2000\Incoming
    • \Program Files\Morpheus\My Shared Folder
    • \Program Files\Grokster\My Grokster
    • \Program Files\ICQ\Shared Files

  5. May overwrite the files in the folders mentioned in step 4, if the files have any of the following extensions:

    NOTE: If the worm overwrites a file, the extension will be changed to .vbs.
    • .mp3
    • .mp2
    • .mpg
    • .mpeg
    • .mpe
    • .avi
    • .mov
    • .dir
    • .jpg
    • .jpe
    • .gif
    • .png
    • .tif
    • .tiff
    • .pic
    • .art
    • .url

      Whether the files are overwritten depends on a random value.

  6. Attempts to email a copy of itself to all the contacts in the Microsoft Outlook Address Book. The appearance of the email message is randomized. The worm sets a registry key after this routine has been executed, so that the emailing process occurs only once.
  7. Attempts to overwrite the files that are part of the following IRC programs:
    • mIRC
    • Pirch
    • Virc
      The modification of the files will cause the worm to spread to other IRC users.

  8. Attempts to create the Install.vbs file on all the mapped drives to which the worm has access.

These instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  1. Update the virus definitions.
  2. Run a full system scan and delete all the files detected as VBS.Caser@mm.
  3. Delete the value:


    from the registry key:

For specific details on each of these steps, read the following instructions.

1. 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 the 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), in the "Protection" section, at the top of this writeup.
  • 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), in the "Protection" section, at the top of this writeup.

    The 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. 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 VBS.Caser@mm, click Delete.

3. Deleting 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 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 the key:

  4. In the right pane, delete the value:

  5. Exit the Registry Editor.

Writeup By: Neal Hindocha