Each time a floppy diskette is accessed, there is a 1 in 512 chance that NYB will send the floppy head from track 0, sector 0 to track 255, sector 62. Under the right circumstances, this action could damage the floppy diskette drive. If a user writes to an infected hard drive just after midnight, the virus crashes the computer. Boot Sector Virus. Form infects floppy diskettes and hard drive boot sectors but does not infect the master boot record.
Form can also randomly destroy files and corrupt data on floppy diskettes.
In addition, Form marks a cluster of sectors as bad and overwrites that cluster with the part of the virus code that would not fit in the boot sector, or Form finds leftover sectors at the end of the physical drive that are not part of a cluster and hides itself there. Boot Sector Virus. AntiCMOS infects floppy diskettes and the partition table of the master boot record on the computer's hard drive. The virus becomes resident at the top sector of the computer's memory when the computer is booted from an infected hard drive. The virus then infects accessed floppy diskettes.