Threat Explorer

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13 February 2007
Also Known As:
VBS/Fireburn.worm, I-Worm.FireBurn

This .VBS worm uses Outlook and mIRC to propagate. It drops the rundll32.vbs file in the Windows folder. If mIRC is installed, it drops the Script.ini file in the mIRC program directory. On June 20th, the worm displays a message and disables the mouse and the keyboard.

Antivirus Protection Dates

  • Initial Rapid Release version 30 May 2000
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 30 May 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.

VBS.Fireburn.A uses Outlook and mIRC to propagate. It drops the file "Rundll32.VBS" in the Windows directory. If mIRC is installed, the worm drops the file "Script.INI" in the mIRC program folder. This worm modifies the following registry keys:
HKLM\Software\Microsoft\Windows\CurrentVersion\Run\MSrundll32 = "rundll32.vbs"
HKLM\Software\Microsoft\Windows\CurrentVersion\RegisteredOwner = "FireburN"

Using Outlook, the worm attempts to email itself to all addresses in the Microsoft Outlook Address Book. The attachment will have one of the following eight names:
The Subject and text of the message vary as follows. If the infected machine has a German version of Windows:
    subject="Moin, alles klar?"
    body="Hi, wie geht's dir? Guck dir mal das Photo im Anhang an, ist echt geil ;) bye, bis dann.."
If the infected machine has a non-German version of Windows:
    subject="Hi, how are you?"
    body="Hi, look at that nice Pic attached ! Watching it is a must ;) cu later..."

Finally, on June 20th, the virus disables the mouse and keyboard by modifying the following registry keys:
HKLM\Software\Microsoft\Windows\CurrentVersion\Run\Shut_Up = "rundll32 mouse,disable"
HKLM\Software\Microsoft\Windows\CurrentVersion\Run\Shut_Up2 = "rundll32 keyboard,disable"

It then displays a message box with the following text:
I'm proud to say that you are infected by FireburN !


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.

If applicable, restore the Script.ini file from backup; otherwise, delete this file. Delete all detected files. Remove the following entries in the registry:
HKLM\Software\Microsoft\Windows\CurrentVersion\Run\MSrundll32 = "rundll32.vbs"