FRISK Software International

Summary of Form.A
Infectable objects: The DOS boot sector on hard drives
Discovered: 15 Jun 1990
Definition files: 15 Jun 1990
Payload: Will cause a 'click' from the PC speaker every time a key is pressed
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Brief description
Technical description

Brief Description
This is a non-remarkable virus from Switzerland, but it is very common.

Technical Description
Form is able to infect hard disks as well as floppies, and stores the rest of itself, as well as the original boot sector on the last track of the hard disk, or in clusters marked as "bad" on a diskette. It contains the following text:

    The FORM-Virus sends greetings to everyone who's reading this text.
    FORM doesn't destroy data! Don't panic! Fuckings go to Corinne.
Unlike most other boot sector viruses, Form infects the DOS boot sector on hard drives instead of the Master Boot Record.

Form is only able to infect a hard disk when you try to boot the machine from an infected diskette. At this time Form infects boot sector, and after that it will go resident to high DOS memory during every boot-up from the hard disk. Once Form gets resident to memory, it will infect practicly all non-writeprotected diskettes used in the machine. Form will create bad sectors on disks it infects.

Form activates on the 18th of any month; on that day it will cause a 'click' from the PC speaker every time a key is pressed. On most machines this activation routine will not be heard, because the routine will fail if a keyboard driver (typically is loaded.

Form is one of the most widespread viruses in existance.

[Analysis: Mikko Hypponen, F-Secure]

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