This book covers what an administrator needs to plan out and integrate a DMZ into a network for small, medium and Enterprise networks. In most enterprises the perception is that a firewall provides a hardened perimeter. However, the security of internal networks and hosts is usually very soft. In such an environment, a non-DMZ system that is offering services to the Internet creates the opportunity to leapfrog to other hosts in the soft interior of your network. In this scenario your internal network is fair game for any attacker who manages to penetrate your so-called hard perimeter.