Virus.MSVisio.Unstable

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: Virus

Viruses replicate on the resources of the local machine. Unlike worms, viruses do not use network services to propagate or penetrate other computers. A copy of a virus will reach remote computers only if the infected object is, for some reason unrelated to the virus function, activated on another computer. For example: when infecting accessible disks, a virus penetrates a file located on a network resource a virus copies itself to a removable storage device or infects a file on a removable device a user sends an email with an infected attachment.

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Platform: MSVisio

No platform description

Description

Technical Details

This is the second macro-virus that also has pretensions to be The Number One in the "Macro.Visio" family. This virus is more complex than Macro.Visio.Radiant - it uses encryption and special tricks to hide its body in infected files.

The virus infects Visio documents, and stencils and templates upon opening an infected document. It enumerates all opened documents, stencils and templates and infects them by coping the virus body into them. To mark already infected documents, the virus writes "Visio2k.Unstable" into their description and does not infect documents with such a mark.

To hide itself, the virus closes all opened widows in the VBA editor, disables Visual Basic Editor's menus and "Standard" toolbar. In case a user tries to edit the macros inside infected documents, he/she will see just the empty editor's main window without any menus, toolbars and child windows.

The virus has a payload that triggers on the 31st, and it displays the message:

  Visio2000.Unstable
   Unstable, it's hard to be the one who's strong
   Who's always got a shoulder to cry on
   Who's got a shoulder for me?

The virus contains three procedures in module "ThisDocument" - "Document_DocumentOpened()", "Unstable()" and "ci()". Inside infected documents second procedure is unreadable because of encryption. The virus decrypts this procedure only just before its call.

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