VBS.Caser@mm

SUMMARY

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.

Protection

• Virus Definitions (LiveUpdate™ Weekly) February 20, 2003
• Virus Definitions (Intelligent Updater) February 20, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Medium
• Large Scale E-mailing: Emails all the contacts in the Microsoft Outlook Address book
• Modifies Files: May overwrite files with certain extensions in some folders

Distribution

• Distribution Level: High
• Subject of Email: Random
• Name of Attachment: Random with a .vbs file extension
• Size of Attachment: 11,793 bytes
• Shared Drives: Copies across mapped drives. Attempts to spread via IRC.

TECHNICAL DETAILS

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:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
2. Adds the value:
   
   Run MSupdt32 wscript %system%MSupdt32.vbs %1
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
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.
     
     NOTES:
     • %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 FilesLimewireShare
   • Program FilesGnucleusDownloads
   • Program FilesGnucleusDownloadsIncoming
   • Program FilesShareazaDownloads
   • C:My DocumentsMy Music
   • C:My Music
   • C:MyMusic
   • C:KazaaMy Shared Folder
   • C:My Downloads
   • Program FilesKazaaMy Shared Folder
   • Program FilesKazaa LiteMy Shared Folder
   • Program FilesBearshareShared
   • Program FilesEdonkey2000Incoming
   • Program FilesMorpheusMy Shared Folder
   • Program FilesGroksterMy Grokster
   • Program FilesICQShared 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.

REMOVAL

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:
   
   MSupdt32.vbs
   
   from the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   

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.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan All 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:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the value:
   
   MSupdt32.vbs
   
5. Exit the Registry Editor.