Which one of these is an example of a malware category?

Malware is a term used to describe any software designed to disrupt, damage, or gain unauthorized access to computer systems. Viruses fall under this definition as they are a specific type of malware that attaches to legitimate software and replicates itself, spreading to other files and systems when the infected software runs. This behavior aligns perfectly with the characteristics of malware, as it is often maliciously crafted to cause harm or exploit systems.

The other options do not represent malware categories. A command line interface is a means of interacting with a computer's operating system using text commands, rather than being malicious software. Spreadsheet software refers to applications used for data organization and analysis, and a database management system is software that allows for the storage, modification, and extraction of data. Both of these serve productive purposes and are not indicative of any malware characteristics.