Computer virus

Computer viruses are categorized into four main types: boot sector, file or
program, macro, and multipartite viruses.

Boot sector viruses are usually transmitted when an infected floppy disk is left
in the drive and the system is rebooted. The virus is read from the infected boot
sector of the floppy disk and transferred to the master boot record of the
system’s hard drive. Then, whenever the computer is booted up, the virus will be
loaded into the system’s memory. Any floppy disk formatted as a bootable disk in
the infected machine would contain the virus and spread itself to other machines.
Program or file viruses are software programs that attach themselves to

executable programs. Once the infected program is run, the virus is transferred to
your system’s memory and may replicate itself further. It may spread to all the
files on a hard drive or to files of a specific type. Common viruses such as
Happy99, Pretty Park, and the ILOVEYOU worm can be classified as this type.

Macro viruses are currently the most commonly found viruses. They infect files
run by applications that use macro languages, like Microsoft Word or Excel. The
virus looks like a macro in the file, and when the file is opened, the virus can
execute commands understood by the application’s macro language. The
infamous Melissa virus is a macro virus as well as the common Laroux Excel
spreadsheet virus.

Multipartite viruses have characteristics of both boot sector viruses and file
viruses. They may start out in the boot sector and spread to applications, or vice
versa.