What best describes a computer virus?

A computer virus is best described as a malicious software program that replicates itself. This definition encapsulates the core nature of a virus, which is designed to spread from one computer to another, often without the user's consent or knowledge. Once a virus infects a host computer, it can attach itself to files and programs, making copies of itself and potentially causing harm by corrupting data, stealing information, or disrupting the normal operation of the system.

Unlike an internet connection, which refers to the method by which computers connect and communicate over the network, or a software update tool, which is intended to enhance functionality and security, a virus specifically aims to proliferate maliciously and compromise systems. Similarly, while operating systems have components that manage software and hardware resources, they do not inherently include viruses, which are unauthorized and harmful programs that users typically do not want or expect to encounter. Thus, the only option that accurately defines what a computer virus is would be the description of it as a malicious software program that replicates itself.