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
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.Read more
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.Description
Technical Details
This Internet worm spreads in e-mail messages using MS Outlook Express as well as MSMAPI service. The worm is written in Visual Basic Script language (VBS).
The worm arrives to a computer as an e-mail message in HTML format or as plain text message with an attached HTML file. In the first case, the script code in the HTML message body automatically executes upon message opening, and the worm gains control. In the other case, a user must open the attached HTML file (double-click on it) to activate the worm.
Being activated, the worm doesn't start immediately spreading; but rather begins infecting a computer.
It modifies the desktop wallpaper with an HTML file that contains the worm code inside. If the desktop has had a background picture before infection, this picture will be shown as the background of the infected HTML and in most cases, it will not be apparent to the user that the wallpaper has been changed; thus, the worm gains control each time the desktop is displayed (for example, upon Window startup) or refreshed.
Additionally, the worm infects all .HTT files in the "WEB" subfolder of the Windows folder. Windows uses these files to customize some folders in view in Explorer when the Web mode is enabled (for example, the Program Files folder). Infection of these files causes the execution of the worm code each time a specific folder is displayed.
Each time the worm gains control, it searches for files with the extensions HTM, HTML, ASP, and VBS and infects them (insert own code into these files) - one file at a time. After some time, all these files on a computer are infected.
The worm also modifies the MS Outlook Express registry values to force Outlook Express created messages in HTML format and uses stationery for this. In this way, the worm spreads in messages created using Outlook Express. Each time Outlook Express composes a new message, it uses one of the stationery templates (just HTML files, infected by the worm - see above); so the worm's script automatically enters a message.
Upon each run, the worm increments a counter in the system registry, and when it reaches value 366, the worm runs one of two spreading routines.
The first routine collects e-mail addresses from the MS Outlook address book and sends infected messages to all collected addresses.
The second routine enumerates all messages in the Inbox folder, and upon each found message, creates and sends "reply", were the subject is "Fw: " and the subject of the original message.
Both routines use MSMAPI service for sending messages.
An infected message has no text, but has the attached file "Untitled.htm" containing the worm code inside.
If the sum of the day and month is 13, the worm searches for EXE and DLL files and deletes them one file at a time.
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