It is important to remember that no computer system can ever be completely secure. The only network, Web site, or computer system that’s 100% secure is one that can’t be accessed by anyone or anything, which makes it completely unusable. Natural disasters, malicious, users who make mistakes, or motivated criminals can compromise security and/or cause damage. The goal for securing your system should be to balance security with accessibility.
Read some basic principles of IT security and computer crime prevention on the ARC Resources page under the heading IT Security:
http://www.arc-tc.com/pages/resources_publications.asp#I
