Internet Security Technologies : Firewall
Written on February 25, 2008 by Jerson
Internet Security Technologies : Firewall
A firewall is an application that allows the user to control and filter packets flowing in and out of the network. Firewalls effectively block probes like ping, operating system fingerprinting, port scans and other types of intrusions. Many companies offer free firewall for personal use only.
A firewall may be software or hardware. A firewall is at the entry point of the network it protects. The most basic firewall performs packet filtering. In packet filtering, the firewall is the first program that receives and handles incoming network traffic and the last to handle outgoing traffic. The policy of filtering the packets may be based on allowing or disallowing packets based on:
- source IP address
- destination port
- protocol
Circuit Relay or Circuit Level Gateway provides additional security. This operates on the Transport Layer. This firewall also determines whether the connection between both ends is valid according to a set of configurable rules. It then opens a session and permits traffic from the allowed source for a limited time period.
Application level gateway acts as a proxy for applications. It performs all data exchanges with the remote system on behalf of the applications. It also allows or disallows network traffic according to specific rules. This is the most secure type of firewall.
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