Security is largely a matter of commonsense. Different people value different things, so there is no single security configuration that will be exactly suited to everyone. However, Fedora Core does a pretty good job out of the box, so most security work will be in fine-tuning your setup to meet particular requirements, rather than urgent actions required to fix glaring security holes.
The most important points for you to try and remember are as follows :
Choose strong passwords.
Avoid using insecure protocols such as Telnet and FTP, if possible.
Do use secure protocols such as ssh and sftp , wherever possible.
Disable network services that are not required.
Configure Tripwire to monitor the integrity of your system on a regular basis.
If you can do all of these things, you can confidently use your Fedora Core 2 system on the Internet, knowing that you re as secure as you reasonably can be, and that all but the most determined hackers will go in search of an easier target elsewhere.