A big reason a lot of people install Linux is for the extra security. While Ubuntu is a pretty secure operating system, new exploits and viruses are found every day. There are still a few simple steps you can take to secure your computer against intruders and internet exploits.
Anti-Virus is a pretty controversial topic on Linux. The popular belief is that Linux is by design immune to virues. Even though your Linux computer may not be infected, you can still host virus infected files. If you are downloading and sharing files via P2P, email or across your network with other Windows computers, anti-virus is essential. The method we take here will not consume vast amounts of system resources that slow your computer down, as is the case with most security suites on Microsoft Windows.
Regardless of operating system any computer connected to the internet should:
1) Install security updates automatically
2) Configure a firewall with a minimal set of rules
3) Install anti-virus software with updated virus definitions and regular scans
4) Protect their browser from XSS and link jacking exploits
This video will show you how to set up all of the above, simply, using only the Linux GUI. No terminal is needed.
This just scratches the surface of securing Ubuntu. Check back later for more advanced topics such as: port scan detection, brute force detection, application profiles, logging and more.