Class Email-Worm
Platform VBS

Technical Details

This is an Internet worm that spreads as a VBS file attached to e-mail messages. To send infected messages, the worm uses MS Outlook. The worm also is able to send its copies to IRC channels by infecting an mIRC client.

When the worm file is activated (by double clicking on the attached file in infected messages, or being accepted as an IRC download), it installs itself into the system by copying its code to the Windows directory with the RUNDLL32.VBS
name and registering it in the auto-run section in the Windows registry:

MSrundll32 = rundll32.vbs

As a result, the worm then activates each time Windows starts up.

E-mail messages

While mailing its copies, the worm connects to MS Outlook, gains access to the address book and sends its copies to all addresses listed in there.
Depending on system configuration, the message has a different Subject and Body. Under the German Windows version, the message appears as follows:

Subject: Moin, alles klar?
Body: Hi, wie geht’s dir?
Guck dir mal das Photo im Anhang an, ist echt geil 😉
bye, bis dann..

Under non-German Windows:

Subject: Hi, how are you?
Body: Hi, look at that nice Pic attached !
Watching it is a must 😉
cu later…

The attached file name is randomly selected from eight variants:


A copy of worm with the same (randomly selected) name is also created in the Windows directory (exactly this copy is attached to infected messages).

IRC infection

To spread to IRC channels, the worm creates a SCRIPT.INI mIRC system file in the mIRC directory (if it is installed). The worm looks for a C:MIRC directory as well as for an MIRC directory in “Program Files”. If mIRC is installed,
the worm drops a new SCRIPT.INI file to there. This file contains a set of instructions that sends the worm file to everybody who enters an infected channel.

The mIRC script also:

  • temporarily moves the worm’s RUNDLL32.VBS file from Windows to the Windows system directory with one of the random names listed above (upon disconnecting from the IRC channel, it moves the VBS file back to the Windows directory with the same RUNDLL32.VBS name)
  • sends the message “Burn, Burn, Burn :)” to a “virus” conference;
  • hides virus-like messages in the current conference (ignores messages that
    contain any of the words: “script”, “virus”, “worm”)

  • upon text “die lamer” in chat, the script quits the channel with the message
    “I’ll commit suicide! R.I.P”

  • upon text “fire”, displays the text “Burn Burn Burn :)”

Payload routine

The payload routine is activated on June 20th. It displays the following message:

I’m proud to say that you are infected by FireburN !

and disables the keyboard and mouse by modifying the following two system-registry keys:

Shut_Up = “rundll32 mouse,disable”

Shut_Up2 = “rundll32 keyboard,disable”


The worm also changes the “Registered Owner” field in
“MyComputer/Properties”, the new value is “FireburN”. This is done by modifying the following registry key:

RegisteredOwner = FireburN

The worm code also contains the “copyright” text:

VBS.FIREBURN.A — mIRC/Outlook worm coded by fireburn
Polymorphic: Changing the actual filename on each start…
greets: to all members of ‘UnCreativeLabs’

Find out the statistics of the threats spreading in your region