Boot sector
From Free net encyclopedia
The boot sector is a region (typically the first 512 bytes) of a hard disk, floppy disk, or similar data storage device, or a partition thereof. Each partition has a boot sector, while the entire disk drive has a master boot record. It is normally the latter to which the term refers, but computers configured to boot multiple operating systems may use the former as well.
The boot sector is loaded to memory and executed as a part of the bootstrap sequence. The boot sector often contains a small computer program that loads the operating system into memory and transfers control to it.
Even floppy disks that lack an actual boot loader normally contain a tiny program that displays an error message, asking the user to insert a bootable disk and press a key. This is a point of vulnerability for a virus to gain control of the system. Virus writers will install a copy of the virus to floppies that are inserted into the computer, which when taken to another computer will infect it. Most computer security experts recommend disabling the ability to boot from floppies in the computer's BIOS, and only enabling it temporarily in the event it's needed. As floppy drives have been deprecated in favor of USB flash drives, BIOS releases have begun to support booting from them, exposing similar risks.