1.1. What is Network Security?

The first step in any discussion about network security is defining network security. If you ask 10 different administrators for a definition of network security you will probably get 10 different answers.

For the purpose of this book the definition that originated from the United States National Security Agency will be sufficient: Network security is the protection of networks and their services from unauthorized modification, destruction, or disclosure. It assures that the network performs its critical functions correctly and there are no harmful side effects.

This is, admittedly, a very broad definition, but a general definition better prepares network administrators to deal with new types of attacks. If a network ...

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