Computer viruses got their name for their ability to “infect” a lot of files on a computer. They also spread to other machines when infected files are sent by email or transferred by users on physical media, for example, on USB drives or (previously) on floppy disks. According to the National Institute of Standards and Technology (NIST), the first computer virus called “Brain” was written in 1986 by two brothers in order to punish pirates stealing software from the company. The virus infected the boot sector of floppy disks and was transmitted to other computers through copied infected floppy disks.

  1. Worms

Unlike viruses, worms do not require human intervention to spread: they infect one computer, and then spread through computer networks to other machines without the participation of their owners. Using network vulnerabilities, for example, flaws in mail programs, worms can send thousands of copies of themselves and infect all new systems, and then the process begins again. In addition to the fact that many worms simply “eat up” system resources, thereby reducing computer performance, most of them now contain malicious “components” designed to steal or delete files.