Boot Diskette

What is a boot sector?
All disks and hard drives are divided into small areas. The first sector is called the boot sector and contains the Master Boot Record (MBR). The MBR contains information about the location of partitions on the disk and reading the boot partition of the operating system. During the boot sequence on a PC running DOS, the BIOS searches for certain system files, IO.SYS and MS-DOS.SYS. When these files were located, the BIOS will search the first sector on the disk or the disk and loads the needed Master Boot Record information in memory. The BIOS passes control to a program in the MBR loads IO.SYS turn. This file shall be responsible for loading the rest of the operating system.

What is a boot sector virus?
A boot sector virus is one that infects the first sector or the boot sector of a floppy or hard disk. boot sector viruses can also infect the MBR. The first PC virus in the wild was Brain, a boot sector virus that exposes stealth techniques to avoid detection. Brain has also changed the volume name of the disk drive.

How to avoid boot sector viruses.
Generally, software applications and subsequent result diskettes infected boot sector infections "shared" diskettes and pirates. It is relatively easy to avoid boot sector viruses. Most are spread when users inadvertently leave floppy in the drive - which happen to be infected with a boot sector virus. The next time they boot their computer, the virus infects the local drive. Most systems allow users to change the boot sequence so that the system is still trying to first boot from the local hard drive (C: \) or CD-ROM.

Disinfecting boot sector viruses.
Boot sector repair is best accomplished by the use of antivirus software. Because some boot sector viruses encrypt the MBR, the incorrect removal can lead to a drive that is inaccessible. However, if you are certain that the virus has affected only the boot sector is not a virus and encryption, the DOS SYS command can be used to restore the first sector. In addition, the DOS LABEL command can be used to restore a damaged volume label and FDISK / MBR will replace the MBR. Neither method is recommended. antivirus is the best tool for cleanly and accurately eliminate boot sector viruses with minimal threat to data and files.

Creating a system disk.
When disinfecting a boot sector virus, the system must always be started from a known clean system disk. On a PC running DOS, a bootable system disk can be created on a system running the exact same version of DOS as the infected PC. From a DOS prompt, type: SYS C: \ A: \ and press ENTER. This will copy the system files from the local hard disk (C: \) to the floppy drive (A: \). If the disk has been formatted using the FORMAT / S will format the disk and transfer the necessary system files. On Windows 3.1x, the disk should be created as described above for DOS-based PC. On Windows 95/98/NT, click Start | Settings | Control Panel | Add / Remove Programs and select the Startup tab. Then click on "Create Disk". Windows 2000 users must insert the Windows 2000 CD-ROM into the CD-ROM, click Start | Run and type the name of the drive followed by bootdisk \ makeboot click OK A: and then. For example: d: \ bootdisk \ makeboot A: Follow the prompts on the screen to finish creating the bootable system disk. In all cases, after the creation of the bootable system disk, the disk must be write-protected to avoid infection.