If not this time, it will be the next. Staying current is extremely important. At times there may be situations when a patch is not available and you want to limit the impact of a vulnerability that may arise. Although beyond the scope of this paper, ipchains should play an important roll in your configuration. Educate yourself - When you have time on your hands, it can be best spent reading articles and white papers that describe how to build and maintain secure networks.
Security requires experience and often a bit of creativity.
Testing your system often reveals vulnerabilities that you may not have been aware of. Here is an excellent paper on NMAP that can get you started. The Ramen worm was successful because of a few factors. Lack of system knowledge Systems are installed using all default values not giving the configuration any thought Passive Administrators Advisories are not monitored and taken into consideration Failure to see significance. Vendor Advisories should be held in high regard and taken seriously Education Security requires constant learning.