By subscribing to the security alert mailing lists, and keeping current, you can do a lot towards securing your computer. If you pay attention to your log files and run something like tripwire regularly, you can do even more.

A reasonable level of computer security is not difficult to maintain on a home computer. More effort is required on business computers, but GNU/Linux can indeed be a secure platform. Due to the nature of GNU/Linux development, security fixes often come out much faster than they do on commercial operating systems, making GNU/Linux an ideal platform when security is a requirement.