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Network Security EssayFirewall-A firewall is a softw ar program or a piece of information that help screen out hackers, virus, worms and Trojan horse that try to reach to your computer over the internet. If you use a computer at home the most efficient and important step to help your computer to protect by turning on your firewall. If you have a more than hotshot computer connects in home. It is important to protect every computer. You should have a hardw atomic number 18 firewall (such as router) to protect your network, but you should also use software firewall on each computer to prevent the spread of virus your network. If your computer is a plane section of business, you should follow the policy established by network administrator. How it works-When your firewall rampart is turned on, everything that goes in and out of the network is monitored. The firewall monitors allows good selective information in and block bad data from entering your network. Firewall uses one or combination of the adjacent method to control the traffic in and of the network- 1) Packet filtering-The most basic form of firewall software uses pre-determined rules to create different filters. If an incoming packet of data (small chunk of data) is flagged by the filters, it is not allowed through. Packets that make it through the filters are sent to requesting system and all others are discarded. 2) Proxy swear outs-A proxy service is an operation that acts as an intermediary between systems. Information from the internet is received by the firewall and sent to the requesting system and vice versa. Proxy server operates at the exercise layer of firewall, where both ends of the connection are forced to conduct session through the proxy. They operate by creating and running a process on the firewall that mirrors a service as if it were running on the host end, and thus centralize all the information transfer to the firewall for examine. 3) Stateful inspection-The most modern method of firewall scanning that does not rely on memory intensive examination is Stateful inspection. A Stateful firewallholds significant attributes of each connection of trusted information for the duration of session. These attributes which are collectively known as state of the connection may include ip addresses, ports involved in the network and number of packets being transferred. Types-There are two types of firewall that are as follows-Hardware firewall.Software firewall.1) Hardware firewall-Hardware firewall built into the device such as routers and can protect every item-by-item machine on a network and require little configuration for efficient work. They mostly use packet filtering technique to examine the header of the packet, find source and destination, then comparing the data to a set of predefine rules, they decide whether to ignore the packet or forward to the next step or to its last destination. 2) Software firewall-Software firewalls are the most popular pr otection method for home users. They usually come as standalone applications or as a part of complete antivirus protection software. That is why it is mostly used in personal network. Antivirus such as bull guard provides besides providing protection for inbound and outward traffic. A software firewall also protects against worms and Trojan horses.The software firewall must be regularly protected to keep up the latest technology updates and provides effective protection. lower-Each type has advantages and disadvantages, ranging from ease of implementation to high initial cost. Companies should use the firewall as part of overall information security program that includes data integrity, application integrity and data confidentiality and authentication.