Merriam Webster’s Dictionary defines “security” as “measures taken to guard against espionage or sabotage, crime, attack, or escape”. Security can be implemented in a variety of ways. With the ever-growing realm of the cyber world, computer security has undoubtedly grabbed the interest of major corporations and civilians alike. Think about the information stored on your personal computer and the massive quantity of personal information on the computers of major corporations. There is a ton of information that none of us want anyone else having access to (i.e. passwords, social security numbers, bank accounts, etc.) Now imagine having all of that information stolen. What would happen? “Identity Theft” is the illegal use of someone else's personal information in order to obtain money or credit. This could easily be obtained from your computer network if the network is not properly secure. (Merriam-Webster, 2007) Networks can be divided into separate layers using the Open Systems Interconnection (OSI) Basic Reference Model. These layers are, from bottom to top, Physical, Data Link, Network, Transport, Session, Presentation, and Application. A layer is a collection of related functions that provides services to the layer above it and receives service from the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of the path. This paper is about examining the security needed to protect each of the first four layers.
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