Computer and network security is a new and fast moving technology and as such, is still being defined. When considering the desired learning outcomes of such a course, one could argue that a network security analyst must be capable of analyzing security from the business perspective in order to adhere to recent security legislation, and from the technical perspective in order to understand and select the most appropriate security solution. Network security  originally focused on algorithmic aspects such as encryption and hashing techniques. While these concepts rarely change, these skills alone are insufficient to protect computer networks. As crackers hacked away at networks and systems, courses arose that emphasized the latest attacks. Currently, many educators believe that to train people to secure networks, they must also learn to think like a cracker [1-2]. The following background information in security helps in making correct decisions: Attack Recognition, Encryption techniques, Network Security Architecture, Protocol analysis, Access control list and vulnerability. For Network security cryptography is present. In cryptography  data that can be read and understood without any special measures is called plaintext or clear text. The method of disguising plaintext in such a way as to hide its substance is called encryption. Encrypting plaintext results in unreadable gibberish called cipher text. We use encryption to ensure that information is hidden from anyone for whom it is not intended, even those who can see the encrypted data. The process of reverting cipher text to its original plain text is called decryption. In cryptography three types of algorithms are present. Symmetric key algorithm, asymmetric key algorithm and hash function.
II LITERATURE SURVEY Susan et.al  concluded that Computer network security is a new and fast moving technology in the field of computer science.