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: JS

JavaScript (JS) is a prototype-based programming language. JavaScript has traditionally been implemented as an interpreted language. The most common use is in web browsers, where it is used for scripting to add interactivity to web pages.


Technical Details

This is a dangerous worm. It replicates using Outlook, Outlook Express and mIRC. The worm is written in JavaScript and Visual Basic Script (VBS). It contains destructive payload routines that are able to format the user's hard disk after reboot, and can delete all files on all available disks.


While installing into the system, the worm creates several files:


Then the worm finds its "already infected" sign in the registry, and if it doesn't exist, the worm creates it.

The infection presence sign is located in the following registry key:


The worm finds all connected network drives and copies itself to them to the following location:

WindowsStart MenuProgramsStartUpMsoe.hta

Spreading via e-mail

The worm uses Outlook and Outlook Express to spread in infected e-mail messages.

Infected message contain the following properties:

Subject: Outlook Express Update
Body: MSNSoftware Co.
Attachment: mmsn_offline.htm

The worm also sends a message that contains the e-mail addresses of its recipients to an e-mail address, which seems to belong to the worm's author.

Spreading via IRC

The worm finds the installation folder of an mIRC client application, and creates there the file name "script.ini". After this, the worm sends itself to each user that joins the same IRC channel where the infected user is.

Filename sent through mIRC: "mmsn_offline.htm"


The worm adds the following line in the file Autoexec.bat:

ECHO y|format c:

This results in formatting disk C: upon computer restarting.

If the day of the month is the 1st, 5th, 10th, 15th or 20th, the worm deletes all files from all drives.

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