V-Sign is another simple boot sector virus, spread on the boot sectors of floppy disks, and infecting the master boot sector of a hard disk when the system is booted from an infected floppy.

The code of many viruses contains bugs, and V-Sign has a bad one - the virus fails to detect that a system is already infected, due to a programming error, and proceeds to infect the system again. This wipes out the saved copy of the original Master Boot Record (MBR) that the virus saves, and thus makes the system unbootable. Since the original MBR code has been lost, it cannot be put back; disinfection must consist of placing a standard MBR back, instead.