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Boot sector virus

(also boot sector infector)

Boot sector virus definition

A boot sector virus is a type of computer virus that infects the boot sector (space reserved for essential instructions on how to start up) of a storage device — typically the master boot record of a hard drive. Boot sector viruses load themselves into the device’s memory as soon as it boots up, before cybersecurity tools have a chance to execute.

See also: Antivirus Scanner, antivirus, anti-malware, stealth virus, bootkit, hard reboot, cold boot, cyberattack

Boot sector virus examples

  • Stoned (1987): One of the earliest boot sector viruses, Stoned infected the boot sector of floppy disks and displayed a message when the infected disk was accessed.
  • Michelangelo (1991): A boot sector virus that was designed to overwrite critical data on the infected hard drive, rendering it unusable. The Michelangelo virus gained media attention because it was set to activate on the 6th of March — the birthday of the famous Renaissance artist Michelangelo.
  • CIH (1998): The CIH virus (also known as Chernobyl) would infect the boot sector of Windows 95 and Windows 98 systems, overwriting their system BIOS on specific dates (such as the 26th of April, the anniversary of the Chernobyl disaster).

Stopping the boot sector virus

  • Use a reputable antivirus. Although antivirus software may not be able to clean up an existing boot sector virus infection (because the virus loads itself into system memory before the antivirus has a chance to start up), it can prevent a boot sector virus from infecting your device in the first place.
  • Regularly update. Keep your device up-to-date with the latest security patches to close off vulnerabilities that boot sector viruses can exploit.
  • Always scan bootable media. Bootable media like USB drives, CDs, or even floppy disks may harbor boot sector viruses, so always scan them with antivirus software before you let them run.
  • Use recovery media. Rescue disks, recovery disks, boot disks, and other forms of recovery media can help you remove a boot sector virus infection from your system.