Lets say I have two internal hard disks, one for the operating system the other for backups. If i make sure to delete the MBR and partition table with dd if=/dev/zero of=/dev/sda bs=512 count=2048 of the disk with the operating system to avoid the possibility of a boot sector virus.

If I reinstall in what ways can that second hard disk be used to cause an infection of the primary disk with the operating system?

I was reading thata boot sector viruses can even spread to other hard drives you have installed or physical media you have plugged into your system.

So what impact can a boot sector virus on a backup drive have on on the primary drive? And any other threats I may have missed? I guess it could effect USB sticks plugged in?

1 Answer 1


Short answer: no.

Long answer: Always take extra precautions.

Boot sector virus only works if you boot up from that particular infected hard drive. If you boot up from the primary drive with Antivirus software, it may detect the secondary hard drive boot sector virus but nothing to worry about.

Nevertheless, to prevent accidentally boot up ANY of the infected drive/media, you should disable the computer BIOS/UEFI option that allows one to select alternate Boot media during computer boot up/power up. Password protect your computer BIOS/UEFI if the computer is also accessible by others.

  • I'm actually using GPT for the primary seems so far gpt bootkits are unconfirmed and gpt doesn't allow executable code. With infected usb/external hard disk if it's connected during starting the computer, is that enough for it to infect the MBR? or do you need to be booting from them specially? i've seen suggestions to never boot with them connected. I saw someone say a bootable usb like live usb if infected will compromise the MBR is that true? i think mostly this doesn't apply if using a GPT as opposed to MBR however still curious.
    – Alister
    Mar 10, 2020 at 11:04
  • @Alister The virus code doesn't work unless a person or process triggers it.
    – mootmoot
    Mar 10, 2020 at 11:56

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