What Is a Firewall?
A firewall is like a border sentry. Think of a firewall as a guard along the border of a country. On a network, a firewall is a filtering device that enforces network security policy and protects the network against external attacks. A packet is a unit of information that is routed between one point and another over the Internet or any other network. The packet header includes information such as source, type, size, and origin and destination address. As a filtering device, a firewall watches for traffic that fails to comply with the rules defined by the firewall administrator.
Firewalls can focus on the packet header, the packet payload (the essential data of the packet) or both; or on the content of a session, the establishment ...
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