A computer virus is typically defined as a malware program that replicates itself by inserting copies or modified copies of itself into other computer programs, data files, or boot sectors of hard drives. When this replication is successful the affected area is said to be infected. The term computer virus is also used in a more broad sense to refer to malware.

Although the technical definitions for the terms computer virus, worm, and malware might overlap in some areas, it’s generally accepted that the first type of computer virus occurred in 1971. In 1971, the internet itself didn’t exist. At the time it was known as ARPANET, this was the scientific military network that preceded today’s internet. This virus was known as the Creeper. Creeper was an experimental self-replicating program that infected DEC (Digital Equipment Corporation) computers across the network. In todays terms, the creeper would be considered a computer worm.

The creeper was written by Bob Thomas at the BBN Technologies lab. Creeper propagated itself throughout ARPANET by exploiting a vulnerability in DEC  computers that were running an operating system known as TENEX operating system. The worm itself wasn’t malicious. It wasn’t designed to do any harm. Upon gaining access to the computer and replicating itself, it would the message broadcast “I’m the creeper, catch me if you can!” on the terminal screen. Consequently, the first virus removal tool, known as  the Reaper,was created. It was designed get rid of the creeper infection.