Threat Explorer

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13 February 2007

VBS.Illen combines features of both a virus and a worm, and acts as a trojan dropper. The Windows Scripting Host (WSH) is required for this virus to replicate. WSH is packaged with Windows98 and Internet Explorer 5, or can be downloaded from Microsoft's web site and installed in Windows95.

Antivirus Protection Dates

  • Initial Rapid Release version 18 December 2000
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 18 December 2000
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date pending
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

This Visual Basic Script virus begins by copying itself to the following locations:
    • c:\windows\system\MyPicture.bmp.vbs
    • c:\WINDOWS\Start Menu\Programs\StartUp\RunDLL.vbs
    • c:\My Documents\MyPicture.bmp.vbs
    • c:\MyPicture.bmp.vbs

Then, the virus overwrites any .vbs file in the following directories with its viral code:
    • c:\
    • c:\My Documents\
    • c:\Windows\
    • c:\windows\samples\wsh\

If mIRC is installed on the target computer, the virus modifies c:\mirc\script.ini and c:\mirc\mirc.ini so that upon connection to IRC, the virus writer is notified of the infected computer's IP address (presumably for use with the trojan program). When joining an IRC channel, the virus tries to send itself to all users in those channels.

Next, the virus modifies the following registry key:
adding the value,

The virus creates a text file named c:\Millennium.NFO in the root directory of the C:\ drive. And finally, a packed version of the trojan program Backdoor.TheThing.c is dropped as "FIX.EXE". A batch file launches the trojan program which then copies itself to the windows folder as c:\windows\explor.exe.

The trojan program then modifies the [boot] section of c:\windows\system.ini, replacing the line:
with the line:
    shell=explorer.exe explor.exe
This ensures the trojan program will run any time a new shell process is created. The trojan program could allow unauthorized users to have remote access to the infected PC.

  • On the 31st of December, the virus will modify the following registry keys with the corresponding values:
    Millennium 0.4b
    Winblows 2000
  • Also, on the 31st, the virus overwrites c:\autoexec.bat with a text message and displays the following dialog box:

The variant VBS.Illen.B is similar to VBS.Illen as mentioned above. It replicates to the same files in the same directories as mentioned above. However, it stops execution at the point where it modifies the c:\mirc\mirc.ini file.


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.

Infected users should do the following:
  • Delete all files detected as VBS.Illen or Backdoor.TheThing.c
  • Restore any .vbs files from a clean backup.
  • Restore c:\mirc\script.ini and c:\mirc\mirc.ini from a clean backup.
  • Delete the c:\...\MyPicture.bmp.vbs value from the HKLM...\RunServices\Winload registry key.
  • Restore the Registry entries modified on December 31st to their correct values (if applicable).