iptables: Creating an open source firewall
With ever-present threats from online attackers and script kiddies, administrators need a firewall on the border of any network. A Linux box can make a particularly effective and capable firewall at a fraction of the cost of a Cisco or Check Point system.
The most obvious use for a firewall is to block unwanted traffic from entering or leaving a network. Firewalls can also make specific connections from outside hosts to internal systems, such as a mail or Web server, either behind the firewall or on a trusted or "de-militarized zone" (DMZ) segment.
By David Coulson at Linux.com
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