What is Firewall? Explain with figure, also define Packet Filtering and Proxy servers !!

Firewall

The firewall is the first line of defense for any computer system or network. All packets that enter the network should come through this point . A modern firewall is a system of application and hardware working together. A sophisticated firewall performs a combination of packet filtering ,network address translation (NAT), and proxy services. These application are depicted in figures respectively.

Firewall have two general methods of implementing security for a network. Although variations between these two exist ,most modifications belongs to one or the other of the following:

— — packet filtering and

— — proxy server (Application Gateway)

Packet Filtering were designed to look at header information of the packet. Packet Filtering, shown in figure 2, was the first type of firewall used by many organizations to protect their network. The general method of implementing a packet filter was to use a router. These routers had the ability to either permit or deny packets based on simple rules.

Proxy Server use software to intercept network traffic that is designed for a given application. The proxy server ,shown in figure 3, recognize the request , and on behalf of the client makes the request to the server. In this internal client never makes a direct connection to the external server. Instead, the proxy functions as man-in-the middle and speaks to both the client and server, relaying the message back and forth. The addition of proxy server capabilities added to the Firewalls created a much more solid security product than a pure packet filter. proxy software can make decisions based on more than the header information of a packet.