April 24, 2008
A firewall is a system that is designed to prevent unauthorized access to or from a private network which can be implemented in both hardware and software or a combination of both. It prevents unauthorized Internet users from accessing private networks to connect to the Internet particularly intranets. Each message passes through the firewall and those that do not meet the specified security criteria are blocked.
Firewall techniques can be any of the following: packet filter, application gateway, circuit-level gateway and proxy servers. In the first technique, each packet entering or leaving the network is examined and is either accepted or rejected based on the user-defined rules. The second technique applies security mechanisms to specific applications. Circuit-level gateway applies security mechanisms when a TCP or UDP connection is established. The last technique intercepts all messages entering and leaving the network and effectively hides the true network addresses.
Leave a Reply