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: 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.Read more
Platform: MSExcel
Microsoft Excel (MS Excel) is a popular spreadsheet program and part of the Microsoft Office productivity suite. Excel files have .xls or .xlsx extensions.Description
Technical Details
This virus infects Excel sheets (XLS files). It contains five macros in one module "Disaster": Auto_Open, Infect, Unvisible, Butterfly, Auto_Close.
While loading an infected document Excel executes auto macros auto_open, and the virus takes control. The virus auto_open macro contains just one command, which defines the Unvisible macro as a handler of OnSheetActivate routine. As a result the virus hooks the sheet activate routine, and while opening a sheet the virus (the Unvisible macro) takes control.
When the Unvisible macro takes control, it executes the Infect macro which infects all active Workbooks. While closing an infected document Excel executes the Auto_Close macro. This macro erases all sheets except having the "Sheet" at the beginning of the name. This macro then saves infected sheet to the Excel Startup directory with the BOOK1.XLS name.
On Monday that falls on 1-5th day or month, or on Friday starting from 25th of month the virus on closing files executes the Butterfly macro that creates new sheet named "A" and deletes all other.
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