Discovered: February 12, 2003
Updated: February 13, 2007 11:42:59 AM
Also Known As: VBS.Cian.C@mm, VBS.Cian.C [CA], VBS_CIAN.C [Trend], VBS/Cian [McAfee]
Type: Worm, Virus
Systems Affected: Windows



VBS.Cian.C is the VBS component inserted into an infected system by the W97M.Cian.C@mm or X97M.Cian.C@mm worm components.

VBS.Cian.C creates and infects various files and modifies several registry values.


Antivirus Protection Dates

  • Initial Rapid Release version February 13, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version February 13, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date February 19, 2003

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

Writeup By: Atli Gudmundsson

Discovered: February 12, 2003
Updated: February 13, 2007 11:42:59 AM
Also Known As: VBS.Cian.C@mm, VBS.Cian.C [CA], VBS_CIAN.C [Trend], VBS/Cian [McAfee]
Type: Worm, Virus
Systems Affected: Windows


When VBS.Cian.C is activated, it does the following:

  1. Copies itself as:
    • %System%\Winstart.vbs
    • %Windir%\Netlnk32.vbs
    • %System%\Wininst32.vbs
    • %System%\Winnt32.vbs
    • %System%\Winnet32.vbs
    • %Windir%\Conversation.vbe (.vbe is not a typo.)

      NOTES:
    • The extension of the file, Conversation.vbe, is correct as shown.
    • %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.
    • %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. Creates these files:
    • %System%\Evade.gif (This is used to infect the Microsoft Excel documents with X97M.Cian.C@mm).
    • %System%\Evade.jpg (This is used to infect the Microsoft Word documents with W97M.Cian.C@mm).

  3. Deletes the file, %XLStartup%\Personal.xls (whereby %XLStartup% is the path to the XLStart folder).
  4. Adds the value:

    Winstart Wscript.exe %sysdir%\Winstart.vbs %1

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  5. Modifies these registry values to:

    Level DWORD:00000001
    AccessVBOM DWORD:00000001

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\%XLAppVersion%\Excel\Security

    NOTE: %XLAppVersion% is a version number, such as 9.0.
  6. Modifies the following registry values to:

    Level DWORD:00000001
    AccessVBOM DWORD:00000001

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\%WordAppVersion%\Word\Security

    NOTE: %WordAppVersion% is a version number, such as 9.0.
  7. Locates every local hard disk (mapped or physical) and does the following:
    • Copies itself to the root of each disk, except the C drive, as X:\Passwords.vbs (whereby X is an arbitrary drive letter).
    • Appends an encoded copy of itself to every .vbs and .vbe file in all the subfolders of each disk, creating the %System%\Winstart.vbs file and modifying the Run key as aforementioned.
  8. Overwrites all the files that have the following extensions, with a copy of itself, as a file that has the .vbs extension:
    • .mp3
    • .mp2
    • .avi
    • .mpg
    • .mpeg
    • .mpe
    • .mov
    • .pdf
    • .doc
    • .xls
    • .mdb
    • .ppt
    • .pps

      if the files are located in any of these folders:
      • C:\Kazaa\My Shared Folder
      • C:\My Downloads
      • %ProgramFiles%\Kazaa\My Shared Folder
      • %ProgramFiles%\KaZaA Lite\My Shared Folder
      • %ProgramFiles%\Bearshare\Shared
      • %ProgramFiles%\Edonkey2000
      • %ProgramFiles%\Morpheus\My Shared Folder
      • %ProgramFiles%\Grokster\My Gorkster
      • %ProgramFiles%\ICQ\Shared Files

  9. Overwrites the file, Script.ini file, if it exists in any of these mIRC folders:
    • C:\Mirc
    • C:\Mirc32
    • %ProgramFiles%\Mirc
    • %ProgramFiles%\Mirc32

      NOTE: %ProgramFiles% represents the Program Files folder, which, by default, is C:\Program Files.

Recommendations

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: Atli Gudmundsson

Discovered: February 12, 2003
Updated: February 13, 2007 11:42:59 AM
Also Known As: VBS.Cian.C@mm, VBS.Cian.C [CA], VBS_CIAN.C [Trend], VBS/Cian [McAfee]
Type: Worm, Virus
Systems Affected: Windows


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.Cian.C.
  3. Reverse the changes made to the registry.
For specific details on each of these procedures, 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.Cian.C, click Delete. If necessary, restore the deleted files from a clean backup.

3. Reversing the changes made to 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_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, delete the value: Winstart
  5. Navigate to the key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\%XLAppVersion%\Excel\Security
  6. In the right pane, delete the value:

    AccessVBOM

    and change the Value Data of:

    Level

    to:

    DWORD:00000003

    (This action signifies the highest security level and it can also be done within Excel.)
  7. Navigate to the key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\%WordAppVersion%\Word\Security
  8. In the right pane, delete the value:

    AccessVBOM

    and change the Value Data of:

    Level

    to:

    DWORD:00000003

    (This action signifies the highest security level and it can also be done within Excel.)
  9. Exit the Registry Editor.



Writeup By: Atli Gudmundsson