With all of the vital personal and business data being shared on computer networks every day, security has become one of the most essential aspects of networking. No one recipe to fully safeguard networks against intruders exists. Network security technology improves and evolves over time as the methods for both attack and defence grow more sophisticated. Network security consists of the provisions and policies adopted by a network administrator to prevent and monitor unauthorized access, misuse, modification, or denial of a computer network and network-accessible resources. Network security involves the authorization of access to data in a network, which is controlled by the network administrator. Users choose or are assigned an ID and password or other authenticating information that allows them access to information and programs within their authority. This practical guide, based on real-world experience of problem-solving in security situations, this work shows how many threats may be countered with good procedures, simple technology and easily-available hardware and software.