Our Networks and computers at home, schools, offices, companies and other places are not secured because a number of confidential transaction occur every second and today computers are used mostly for transaction rather than processing of data, so Data security is needed to prevent hacking of data and to provide authenticated data transfer. Data security can be achieved by Firewall; a firewall is typically placed at the edge of a system and acts as a filter for unauthorized traffic. But conventional firewalls rely on the notions of restricted topology and controlled entry points to function. In most systems today, the firewall is the machine that implements the “security policy” for a system. Firewall establishes a barrier between a trusted, secure internal network and another network (e.g., the Internet) that is assumed not to be secure and trusted. Distributed firewall is a mechanism to enforce a network domain security policy through the use of policy language Security policy is defined centrally. Distributed firewalls secure the network by protecting critical network endpoints, exactly where hackers want to penetrate. It filters traffic from both the Internet and the internal network because the most destructive and costly hacking attacks still originate from within the organization. This paper will introduce the concept of distributed firewall as a security policy of local networks. I will study Distributed firewall because it gives total security to a network.

Local Networks, Security Policy, Firewall, Distributed Firewall