What is Boot Sector Virus & How to Prevent Them?


When it comes to strengthening cybersecurity and protecting your digital data, you must be able to recognise a few more names and terms than what you already know about the digital risks and dangers, a specific one being “computer viruses”. So, before we dive into the definitions of boot sector virus, it’s imperative to understand how a basic virus works and what it is.

In simple terms, a virus is a malicious program that tries to disrupt a normal computing operation by spreading its infectious codes into different executable files of the hijacked system. By multiplying itself, the creator of that virus can secure vulnerabilities and proceed with their intentions of extracting private information, gaining admin control, and similar spiteful purposes.

Viruses are usually transmitted through defective online software, websites, emails, links, etc., and occasionally, by infected outside drives. Recently, however, cybercriminals have been involved in the increased practice of physical virus infections, more often through removable disks and devices. Boot sector virus is a similarly conducted malware, more of which we’re going to discuss below.

What is Boot Sector virus?

A boot sector virus, also known as an MBR virus, DBR virus, or a boot infector, is a type of virus that explicitly targets and contaminates a specific physical segment containing essential information of the computer required to properly run the operating system for start-ups and to operate initial functions. 

It is an extremely dangerous malware that takes over the DOS boot sector or Master Boot Record (MBR) of a floppy drive or hard disk. Almost all boot sector viruses can not only infect the boot sector but can also encrypt the MBR, which could result in severe dysfunction of the entire computer system.

Once infected, boot sector viruses usually operate by performing a hard disk’s boot sector replacement with malicious copies of codes that are written and commanded to run every time you try to reboot the system, start up the computer, or open specific software. It can effectively save itself into the memory and pollute the non-infected drives read by the system.

Types of Boot Sector Viruses

Boot viruses can be sub-divided into several types based on their target and how they affect that sector when attacking a system. They can either alter the Floppy Boot Record (FBR), the DOS Boot Record (DBR), or the Master Boot Record (MBR).

The Master Boot Record, occasionally known as the ‘partition sector’, confirms the OS location and is often found on “Track 0”. It contains the Disk Signature, the Partition Table, and the Master Boot Code.

The DBR is routinely situated into numerous segments after the MBR and holds the vital information for loading the operating system from the hard drive into the computer’s main memory, providing control to the loaded program. The Floppy Boot Record (FBR), or the third sector, performs functions somewhat similar to the DBR.

The next categorising method would be to look at their behaviour. For example, some boot viruses overwrite the DBR, MBR, or FBR sector with their own code, while others relocate the original data somewhere on the floppy or hard drive. Either way, the hard drive sectors could be entirely damaged, or all the data could get corrupted, making them unreadable.

How Does Boot Sector Virus Infect a Computer?

Despite their different behaviours, all types of boot viruses have one similar feature; they’re memory-resident, meaning that a boot virus loads itself into the infected system's memory to interrupt the booting process. But how does one infect a system in the first place?

The most typical way of a boot sector virus transmission is through physical media. For instance, when you connect an infected USB flash drive or floppy disk to your computer, the system reads the volume boot record (VBR) of that disk. During the process, the external disk transfers data and then replaces or modifies the original boot code.

Then, every time you try to start up the infected computer, the boot virus code will immediately get loaded into the memory and start running as a part of the master boot record. After that, it will proceed to deceive the System BIOS operation into continuing its residence in the memory.

Once establishing itself there, the virus will begin to check the admission or disk entry and spread its malicious codes on different boot sectors and other removable physical disks and media connected to the computer. It can also be transmitted along with the shared network through downloaded files, software, and email attachments.

How to Prevent Boot Sector Virus?

Modern operating systems and computers include advanced protection against boot sector viruses, making them less common nowadays. However, it would be best if you remain extra cautious in case of possible infection. Boot Sector Virus prevention is all about using proper strategies and following safe digital practices. Below are some tips that can help you do that:

  1. Use robust Antivirus Software: Every user should install a strong antivirus program that can help protect their devices from all types of viruses and online threats, including the boot sector virus. A powerful security software will be able to scan, detect, and remove any potential malware that you might encounter online or through connected external disks. 
  2. Back up all your data: Boot sector virus infection can lead to data loss through corruption or extraction of your essential information. That’s why you must regularly back up your crucial files and data to regain them in case you face a similar situation. You should also scan the backed up data before running them into your computer. 
  3. Frequently update your systems and software: Outdated operating systems and software may hold security gaps and vulnerabilities, making them unable to combat the latest versions of boot sector virus and other malware. So, keep your systems and antiviruses up to date for filling those holes and strengthening your against possible boot virus interaction.
  4. Never download from unsecure sites and sources: Many users are tempted to download pirated software, movies, and so on from torrent sites. Unfortunately, they don’t realise that these websites are the primary source of virus infection into your device and other connected disks. Therefore, you must avoid unsecure downloads and always check if a site you’re visiting is legitimate or not. 
  5. Do not trust suspicious removable media: Another major source of boot virus transmission is USB and external hard drives. Always make sure to scan any removable media before connecting them into your system, and never plug them before starting up the computer. If the USB seems suspicious, do not use it on any of your devices. 
  6. Avoid unknown emails: Sometimes, hackers may masquerade as legitimate officials or your friends to trick you into clicking an infectious attachmortonent or link that might take you to a malicious website. Following this could infect your device with a boot virus. So, ignore and report any emails that seem strange or fishy. 
  7. Use firewalls: When you’re connected to the internet, cybercriminals could intrude on your computer by attacking with viruses and malware. Firewalls monitor the data you send and receive through the connected network and constantly scan for these threats. Using this feature could help your device protect against Boot Sector Viruses. 
  8. Be wary of public networks: Boot Sector Viruses are well-known to be transferred from one device to another associated with the same network. More specifically, public Wi-Fi networks pose more danger of getting your device contaminated, as there will be unknown users and equipment connected to that network. So, avoid such networks and enable a VPN while using them. 
  9. Quarantine infected drives and devices: If you suspect your computer or hard drive to contain the boot sector virus, immediately isolate them from other devices. This means you have to log out of all the networks your device is
    connected to and prevent plugging the infected USB drives into other computers until thoroughly disinfecting them.


Although viruses are extremely damaging, the majority of computer users seem to ignore the possibility of encountering these infections, which makes them even more vulnerable. Boot sector viruses are one of those threats that could ultimately damage your entire system and destroy the important data stored in them. Ignoring a boot virus may result in OS failure and many other consequences.

So, in conclusion, you must remain extra aware of your digital activities that could lead to boot sector virus infections. Secure your computers and hard drives with a powerfu  antivirus, such as Norton Security, that regularly scans them for malware. Avoid downloading pirated files or plugging stranger USB disks into your devices, and keep them free from boot viruses.

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Editorial note: Our articles provide educational information for you. Our offerings may not cover or protect against every type of crime, fraud, or threat we write about. Our goal is to increase awareness about Cyber Safety. Please review complete Terms during enrollment or setup. Remember that no one can prevent all identity theft or cybercrime, and that LifeLock does not monitor all transactions at all businesses. The Norton and LifeLock brands are part of Gen Digital Inc. 


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