Here is a good paper that was published earlier this year. It provides an interesting perspective on network security. "Information systems security. Computer and network security. Internet security. It's a complex world, and growing more so every day. With these changes, some truths and approaches to security remain the same, while others are new and radically different. Developing a sound security strategy involves keeping one eye on the reality of Internet-speed changes in threats and technology, and the other on the reality of the corporate environment. Purchasing security devices is easy.
Knowing how and what to protect and what controls to put in place is a bit more difficult. It takes security management, including planning, policy development and the design of procedures."