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/etc/rc.conf

firewall_enable="YES"
firewall_type="open"
firewall_script="/etc/ipfw.rules"

/etc/ipfw.rules

#!/bin/sh
ipfw -q -f flush  
oif="xl0"           
cmd="ipfw -q add "    
ks="keep-state"       
$cmd 00100 pass all from any to any via lo0 #localhost
$cmd 00101 deny all from any to 127.0.0.0/8
$cmd 00102 deny all from 127.0.0.0/8 to any
$cmd 00500 check-state
$cmd 00502 deny all from any to any frag
$cmd 00501 deny tcp from any to any established
$cmd 00600 allow tcp from any to any out via $oif setup $ks
$cmd 00601 allow udp from any to any out via $oif $ks
# allow in to www & ssh
$cmd 00700 allow tcp from any to any 80 in via $oif setup $ks #www
$cmd 00701 allow tcp from any to any 22 in via $oif setup $ks #ssh
# ping
#$cmd 02000 allow icmp from any to any out icmptype 8
#$cmd 02001 allow icmp from any to any in icmptype 0
$cmd 02000 allow icmp from any to any