The bottom line is that there is no such thing as a secure operating system, firewall or not. What is required is a persistent mixture of vigilance and adaptability. Many perceive security as synonymous with network privacy or prevention of network intrusion. Privacy is one aspect of security, but it is not the network that is our special enemy. Many breaches of security happen from within.
Software security is a vast subject because modern computer systems are complex.
It is only exacerbated by the connectivity of the Internet, which allows millions of people to have a go at breaking into networked systems. What this points to is the fact that a secure environment requires a tight control of access control on every host individually, not merely at specific points such as firewalls. This series of articles is an attempt to illustrate how cfengine can be used to help you automate a level of host integrity on all the hosts of your network. Cfengine is a network-configuration tool with two facets. An expert system describes the way you would like your hosts and network to look and behave.