Network security goes hand in hand with computer security, and these days it's hard to separate the two. Everything, from electronic hotel door locks to cellular telephones to desktop computers, is attached to networks. As difficult as it is to build a secure stand-alone computer, it is much more difficult to build a computer that is secure when attached to a network. And networked computers are even more pregnable; instead of an attacker needing to be in front of the computer he is attacking, he can be halfway across the planet and attack the computer using the network. A networked world may be more convenient, but it is also much more insecure.
These days it's pretty much impossible to talk about computer security without talking about network security. Even something as specialized as the credit card clearing system works using computer networks. So do cellular telephones and burglar alarm systems. Slot machines in casinos are networked, as are some vending machines. The computers in your kitchen appliances will soon be networked, as will the ones in your car. All computers will eventually be networked.
Lots of different types of networks are out there, but I'm going to spend the most time talking about the Internet protocol: TCP/IP. Networking protocols seem to be converging on the Internet, so it makes the most sense to talk about the Internet. This is not to imply that the Internet protocols are more insecure than others—although certainly they were never ...