ABSTRACT
The Perimeter security, usually a firewall, is the first line of defense in asset and resource protection. Firewalls are a key component in security arsenal. In general, a firewall is a device or set of devices that restrict access between trusted and untrusted networks. Firewalls form the base of physical infrastructure. The three main firewall technologies are packet filter, proxy, and stateful inspection. Packet-filtering systems route packets between trusted and untrusted networks. The packet filters were implemented mainly on routers and filtered packets using such characteristics as the destination Internet Protocol address. Packet filters have a few attributes that do not make them ideal as the sole perimeter security device, such as difficulty in checking and filtering User Datagram Protocol packets. Proxy servers help improve perimeter security by watching the application layer, providing security to the communications that take place. The major firewalls on the market are Check Point’s Firewall–1 and Cisco’s PIX, both stateful–inspection firewalls.
