A technical definition of a virus is a segment of program code that implants itself to one of the executable files and spreads systematically from one file to another. In layman’s term, a virus is a piece of software designed and written to adversely affect a computer by altering how it works without the owner’s knowledge or permission. Computer viruses are written and have a specific purpose and never spontaneously generate.

A virus may self-replicate and propagate as it spreads itself from one file to another without the user’s input or knowledge. It can also implement the symptom or damage planned by the perpetrator which could include erasing a disk, corrupting programs or simply creating havoc on a computer. Computer viruses can either be benign or malignant. A benign virus does not do any real damage to a computer except to display some sort of unsolicited message. A malignant virus, on the other hand, seeks to inflict malicious damage.