Computers and Networking have become inseparable by now. A number of confidential transactions occur every second and today computers are used mostly for transmission rather than processing of data. So Network Security is needed to prevent hacking of data and to provide authenticated data transfer. Network Security can be achieved by Firewall. Conventional firewalls rely on the notions of restricted topology and controlled entry points to function. Restricting the network topology, difficulty in filtering of certain protocols, End-to-End encryption problems and few more problems lead to the evolution of Distributed Firewalls. A distributed firewall is a mechanism to enforce a network domain security policy through the use of a policy language, a policy distribution scheme enabling policy control from a central point and certificates, enabling the identification of any member of the network policy domain. 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.They provide virtually unlimited scalability. In addition, they overcome the singlepoint-of-failure problem presented by the perimeter firewall. In our paper we deal with distributed firewall concepts, its evolution, its components, policies and a sample of the designed policy along with implementation. A distributed firewall gives complete security to the network. 1.Introduction :
Distributed firewalls are host-resident security software applications that protect the enterprise network's servers and end-user machines against unwanted intrusion. They offer the advantage of filtering traffic from both the Internet and the internal network. This enables them to prevent hacking attacks that originate from both the Internet and the internal network. This is important because the most costly and destructive attacks still originate from within the organization. They are like personal firewalls except they offer several important advantages like central management, logging, and in some cases, access-control granularity. These features are necessary to implement corporate security policies in larger enterprises. Policies can be defined and pushed out on an enterprise-wide basis. A feature of distributed firewalls is centralized management. The ability to populate servers and end-users machines, to configure and "push out" consistent security policies helps to maximize limited resources. The ability to gather reports and maintain updates centrally makes distributed security practical. Distributed firewalls help in two ways. Remote end-user machines can be secured . Secondly, they secure critical servers on the network preventing intrusion by malicious code and "jailing" other such code by not letting the protected server be used as a launch pad for expanded attacks. Usually deployed behind the traditional firewall, they provide a second layer of defense. They work by enabling only essential traffic into the machine they protect, prohibiting other types of traffic to prevent unwanted intrusions. Whereas the perimeter firewall must take a generalist, common denominator approach to protecting servers on the network, distributed firewalls act as specialists. 2.Evolution of Distributed Firewall from the Conventional Firewall : A firewall is a collection of components, interposed between two networks, that filters traffic between them according to some security policy.
Basic structure of a firewall...