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Firewalling with OpenBSD's PF packet filter

Post date: April 19, 2005, 02:04 Category: Views: 6445 Comments
Tutorial quote: PF operates in a world which consists of packets, protocols, connections and ports.

Based on where a packet is coming from or where it's going, which protocol, connection of port it is designated for, PF is able to determine where to lead the packet, or decide if it is to be let through at all.

It's equally possible to direct network traffic based on packet contents, usually referred to as application level filtering, but this is not the kind of thing PF does. We will come back later to some cases where PF will hand off these kinds of tasks to other software, but first let us deal with some basics.

We've already mentioned the firewall concept. One important feature of PF and similar software, perhaps the most important feature, is that it is able to identify and block traffic which is you do not want to let into your local network or let out to the world outside. At some point the term 'firewall' was coined.


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