Virus.DOS.Hymn

Detect Date 01/12/2001
Class Virus
Platform DOS
Description

This is a very dangerous encrtypted memory resident parasitic virus. It hooks INT 21h, and writes itself to the end of COM and EXE files that are executed, closed, renamed or when the file attributes are changed.

When the date and month correspond in number (January 1st, February 2nd,…), this virus destroys a part of the system information in the C: disk boot sector, then it plays the former USSR national anthem, and decrypts and displays the picture.

When corrupting the boot sector, the virus sets the bytes to zero in the boot sector that contains the number of bytes in a sector, number of sectors in a cluster, number of FAT copies, etc – a total 9 bytes. If the boot sector of a computer running in the MS-DOS environment is changed in such a way, the computer remains unbootable both from the hard disk and the floppy drive. To restore information, it is necessary to use special utilities.