Parent class: VirWare

Viruses and worms are malicious programs that self-replicate on computers or via computer networks without the user being aware; each subsequent copy of such malicious programs is also able to self-replicate. Malicious programs which spread via networks or infect remote machines when commanded to do so by the “owner” (e.g. Backdoors) or programs that create multiple copies that are unable to self-replicate are not part of the Viruses and Worms subclass. The main characteristic used to determine whether or not a program is classified as a separate behaviour within the Viruses and Worms subclass is how the program propagates (i.e. how the malicious program spreads copies of itself via local or network resources.) Most known worms are spread as files sent as email attachments, via a link to a web or FTP resource, via a link sent in an ICQ or IRC message, via P2P file sharing networks etc. Some worms spread as network packets; these directly penetrate the computer memory, and the worm code is then activated. Worms use the following techniques to penetrate remote computers and launch copies of themselves: social engineering (for example, an email message suggesting the user opens an attached file), exploiting network configuration errors (such as copying to a fully accessible disk), and exploiting loopholes in operating system and application security. Viruses can be divided in accordance with the method used to infect a computer:
  • file viruses
  • boot sector viruses
  • macro viruses
  • script viruses
Any program within this subclass can have additional Trojan functions. It should also be noted that many worms use more than one method in order to spread copies via networks.

Class: Email-Worm

Email-Worms spread via email. The worm sends a copy of itself as an attachment to an email message or a link to its file on a network resource (e.g. a URL to an infected file on a compromised website or a hacker-owned website). In the first case, the worm code activates when the infected attachment is opened (launched). In the second case, the code is activated when the link to the infected file is opened. In both case, the result is the same: the worm code is activated. Email-Worms use a range of methods to send infected emails. The most common are: using a direct connection to a SMTP server using the email directory built into the worm’s code using MS Outlook services using Windows MAPI functions. Email-Worms use a number of different sources to find email addresses to which infected emails will be sent: the address book in MS Outlook a WAB address database .txt files stored on the hard drive: the worm can identify which strings in text files are email addresses emails in the inbox (some Email-Worms even “reply” to emails found in the inbox) Many Email-Worms use more than one of the sources listed above. There are also other sources of email addresses, such as address books associated with web-based email services.

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Platform: VBS

Visual Basic Scripting Edition (VBScript) is a scripting language interpreted by Windows Script Host. VBScript is widely used to create scripts on Microsoft Windows operating systems.


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:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion 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'

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