Network security is a complicated subject, historically only tackled by well-trained and experienced experts. However, as more and more people become “wired”, an increasing number of people need to understand the basics of ecurity in a networked world. It explains the concepts needed to read through the hype in the marketplace and understand risks and how to deal with them.

Some history of networking is included, as well as an introduction to TCP/IP and internetworking. We go on to consider risk management, network threats, firewalls, and more special-purpose secure networking devices.

This is not intended to be a “frequently asked questions” reference, nor is it a “hands-on” document describing how to accomplish specific functionality. It is hoped that the reader will have a wider perspective on security in general, and better understand how to reduce and manage risk personally, at home, and in the workplace.  The computer is the great invention of 20thcentury which has been now the part of our life. Gradually it became necessary to connect different computers that lead to establish local network. The network field grew up by eaps and bound that lead to huge matrix of computer network. This great invention is known as Internet. It benefited to human being in each & every field, which is now part of our life. But as we know each coin has two sides.

Similarly the darkness of network field is an unimaginable. For example whenever you connect to your internet, you provide “Gateway” to the hackers & crackers who are wiling to enter your machine thus whenever you connect to internet your machine is not secure at all.