This document provides an overview of computer security. It discusses why security is important given the dangers posed by unauthorized access to computers and networks. It outlines what aspects need to be secured, including physical access, user accounts, monitors, networks, data encryption, and more. The document also covers potential losses from security breaches like lost data, identity theft, and reputation damage. It provides a basic computer security checklist for securing operating systems, antivirus software, firewalls, backups, and other aspects.