Question

A file infector virus can infect floppy and hard disk

Answer 1

Floppy disks, despite the fact that they are now quite obsolete technology, are still probably the number one way that viruses are spread (although I think the Internet and networking in general are overtaking them quickly). Floppies are a major source of virus infection for two main reasons: first, because they are used to carry files from PC to PC, and second, because they are the only way that boot sector infector viruses can be transmitted.

Answer 2

A boot sector virus is a type of virus that infects the boot sector of floppy disks or the Master Boot Record (MBR) of hard disks (some infect the boot sector of the hard disk instead of the MBR). The infected code runs when the system is booted from an infected disk, but once loaded it will infect other floppy disks when accessed in the infected computer. While boot sector viruses infect at a BIOS level, they use DOS commands to spread to other floppy disks. For this reason, they started to fade from the scene after the appearance of Windows 95 (which made little use of DOS instructions). Today, there are programs known as ‘bootkits’ that write their code to the MBR as a means of loading early in the boot process and then concealing the actions of malware running under Windows. However, they are not designed to infect removable media.

The only absolute criteria for a boot sector is that it must contain 0x55 and 0xAA as its last two bytes. If this signature is not present or is corrupted, the computer may display an error message and refuse to boot. Problems with the sector may be due to physical drive corruption or the presence of a boot sector virus.