A boot sector is a part of a disk that contains code to start programs and reference key features. There are two types: master boot record and volume boot record. A virus can replace the boot sector code, causing damage. Removing it requires a good antivirus program.
A boot sector is the part of a hard drive or floppy disk where code is stored to start special programs and to reference other key features to keep the disk running. There are many types, but there are two main ones: the master boot record and the volume boot record. A master boot record exists on a drive that has been partitioned and usually finds the active partition and runs its own volume boot record. The volume boot record, in turn, often contains the code to run the operating system on your computer.
Hard disk drives contain a master boot record as the first boot sector, while floppy disks or USB disks usually contain only a volume boot record as the first boot sector, since they cannot be partitioned. A computer’s BIOS, the part that runs before all else, immediately looks to this sector of a drive, whether it’s a master or a volume, for instructions on what to do next. The boot sector can actually include instructions for doing quite complex things, which are used for things like giving a user the ability to run one of many operating systems, but it also means that there is the potential for abuse in the form of a virus.
To be a boot sector, the sector must meet only one criterion, which is to have a 0xAA55 signature as the last two bytes. Not having this signature can cause an error and the computer may not finish booting. This can happen for a variety of reasons, including a virus or simply a bad sector from a physical error on the drive itself.
This type of virus is simply one that replaces the normal boot sector code with a code of its choosing. Since the boot sector loads every time a computer starts up, such viruses can be incredibly destructive and in some cases can be quite difficult to remove properly. Since the virus is loaded into memory as soon as the computer starts up, it can also spread quite easily to every drive or disk that the infected computer comes into contact with.
The most common way a boot sector virus spreads is by leaving an infected disk in a computer’s disk drive. On the next boot, the BIOS reads that disk’s volume boot record, receives the virus, and passes it into memory. From there it can spread to other drives and to other inserted disks. However, a virus can also be transmitted over a network if it is not properly protected, and can also be transmitted as an attachment to an email.
Removing a boot sector virus requires a good antivirus program. Many encrypt the boot sector when they infect it, so it’s not easy to remove the virus. For this reason, it is important to use a good antivirus program that has a record of many of these viruses and can then carefully remove the virus without causing harm to your computer.
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