Guide to Unix/BSD/OpenBSD/As a Firewall

OpenBSD includes PF ("packet filter") as a firewall. Getting Started To turn PF on, on boot up, create the configuration file rc.conf.local. vi /etc/rc.conf.local To activate PF on boot up enter the following in the configuration file: pf=YES To enable PF manually, enter in the following command: pfctl -e To disable PF manually, enter in the following command: pfctl -d Congratulation, you are now protected by one of the best firewalls available. Configuring PF Pf is a very good firewall by default however it also contains a few options. You can change the configuration of pf by editing the configuration file /etc/pf.conf. Options Option Description Example Description of ExamplerdrRedirects trafficrdr on tl0 proto tcp from any to any port 80 -> 192.168.1.20 Redirects traffic for 192.168.1.20 on the tl0 interface, for any port up to 80. BlockBlocks trafficblock out on fxp0 from 192.168.0.1 to anyFor 192.168.0.1, blocks outgoing traffic on the fxp0 interface for any port.PassAllows traffic to pass throughpass in allUnless stated otherwise, pf will allow all incoming traffic.ScrubScrubing defragments and in some cases rejects fragmented packets.scrub in allscrubs all incoming traffic on all interfaces.Tabledefines groups of IPs.table <goodguys> { 172.16.0.0/16, 172.16.1.0/24, 172.16.1.100 } block in on dc0 all pass in on dc0 from <goodguys> to anyAllows incoming connections to <goodguys> on the dc0 interface. Blocks all other incoming connections on the dc0 interface. Wrong information. Scrubbing Scrubbing defragments and in some cases rejects fragmented packets. This prevents your computer from becoming fragmented, however it also causes a lot of packets to be lost. To scrub an network interface enter the following in you /etc/pf.conf: scrub <in/out> <interface> A simple example of this is scrubbing all of the incoming interfaces. scrub in all Authors If you made a contribution to this article please feel free to add your username. CFeyecare- Started page. See Also PF on Wikipedia small guide to PF usage on freebsd to fight spam References "Faq pf." Pf. OpenBSD. 3 Nov. 2008 <http://www.openbsd.org/faq/pf/>.