The Firewall is the software which runs on different computers to inspect traffic of network passing through it. It allows passing or denies according to the rules set up. It provides the protection to the networked computers from the hostile intrusion, because the intrusions interrupt the service or corruption of data. The Firewall can be software program or hardware device which runs on the secure host of the computers. Usually it has two network interfaces, first one for the protection and the second one to expose. The firewall is in the mid point of the two networks.

The firewall segment the network into many physical subnetworks limiting the damage from spreading to another subnet. The firewall gives protection to private local area network from the hostile intrusion through the internet. It allows the network administrators in offering access to the specific types of the internet services to the concerned local area network users. It is the most essential part of the information management system. The privileges are given as per the description of the job. There are four different types of firewall like circuit level gateways, packet filters, stateful multilayer firewall for inspection and the application level gateways respectively.