Email-Worm.VBS.Horillka

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.

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 malicious worm spreads via the Internet in the form of a file attached to infected messages. It is an encoded VBS script of 25562 bytes.

When downloaded Horilka decrypts itself.

It copies itself to the Windows system directory under the name WinSys32dll.vbs, and registers this file in the system registry autorun key.

HKLMSoftwareMicrosoftWindowsCurrentVersionRunWinSys32dll.

The virus mass mails all addresses found in the Microsoft Outlook address book.

Characteristics of infected messages:

Message header:

��������!

Message body:

�������� ����� vbs ���������� ��� ������ ������� � ������ �� Windows!
��� �������� �������� � ��������, �������������� �� �����.
������������ ������ ������� �� ������-�����, ��� �������� �������������
vb � js ������, ������ ��� ��� ������ ������������� ������������.
���������� ������� ���� � ��������� �� ���������� ������� �������� �����
����������� �������� � ������ ����������.

Attachment:

a VBS script,

WinSys32.dll.vbs

Once messages have been sent, the virus sends its author a message which includes all .pwl (password) files found in the Windows directory.

Messages are sent once, when each user's configuration is loaded.

The virus copies itself to all disks and all directories under the name of Folderdll.vbs and marks these files as hidden.

It searches the Windows folder for files with the following extensions:

.vbs
.jpg
.jpeg
.gif
.bmp
.htm
.html
.avc
.txt
.doc
.mp3
.wav
.dbf

Horilka overwrites .vbs files with its own code.

It replaces .jpg, .jpeg, .gif and .bmp files with a GIF format graphic contained in the body of the virus.

It adds the following code to .htm and.html files: