Once you get your OS installed, it's imperative that you secure your installation. As Jon Griffin repeatedly warns us, "No distribution is secure out of the box." The Reference Platform implements some basic precautions, but security is a process, not a condition. If you are responsible for a computer hooked to the internet, you are responsible for learning some rudiments of security, such as monitoring the state of a computer, maintaining patch levels, and keeping backups. We recommend these resources: