What is a virus?

A computer virus is simply a computer program that executes malicious code on your machine.

To make the concept of a virus simple to understand, consider this example. A computer program has a particular function. Microsoft Word, for example, is a text editor program. Excel is a program for creating spreadsheets. A virus is also a program, except its function is to perform tasks that delete your files, steal passwords from your computer, and many others.