In recent times, the worldwide network connection is beginning to play a more important role in our lives. Since the modern societies are full of growing number of cyber crimes, network security seems to be a necessity in normal life.
There are various definitions of ¡§network security¡¨. The American National Standard defines Network security as a ¡§Protection of networks and their services from unauthorized modification, destruction, or disclosure.¡¨ The standard also mentions that the network security ¡§provides assurance the network performs its critical functions correctly and there are no harmful side-effects¡¨. (1)