Ipfwm

Copy default kernel file:
# cd /usr/src/sys/i386/conf
# cp GENERIC IPFWKERNEL

edit kernel

# vi IPFWKERNEL

sertakan file berikut:
options IPFIREWALL # required for IPFW
options IPFIREWALL_VERBOSE # optional; logging
options IPFIREWALL_VERBOSE_LIMIT=10 # optional; don't get too many log entries
options IPDIVERT # needed for natd

kemudian build kernel tersebut
# cd /usr/src
# make buildkernel KERNCONF=IPFWKERNEL

Install kernel tersebut:
# make installkernel KERNCONF=IPFWKERNEL

 reboot the system:
# reboot

buka file /etc/rc.conf file
# vi /etc/rc.conf

sertakan settings dibawah ini:
firewall_enable="YES"
firewall_script="/usr/local/etc/ipfw.rules"

jika belum jelas lihat disini

kemudian buat skrip dengan nama file /usr/local/etc/ipfw.rule:
# vi /usr/local/etc/ipfw.rules
Append following code:

IPF="ipfw -q add"
ipfw -q -f flush

#loopback
$IPF 10 allow all from any to any via lo0
$IPF 20 deny all from any to 127.0.0.0/8
$IPF 30 deny all from 127.0.0.0/8 to any
$IPF 40 deny tcp from any to any frag

# statefull
$IPF 50 check-state
$IPF 60 allow tcp from any to any established
$IPF 70 allow all from any to any out keep-state
$IPF 80 allow icmp from any to any

# open port ftp (20,21), ssh (22), mail (25)
# http (80), dns (53) etc
$IPF 110 allow tcp from any to any 21 in
$IPF 120 allow tcp from any to any 21 out
$IPF 130 allow tcp from any to any 22 in
$IPF 140 allow tcp from any to any 22 out
$IPF 150 allow tcp from any to any 25 in
$IPF 160 allow tcp from any to any 25 out
$IPF 170 allow udp from any to any 53 in
$IPF 175 allow tcp from any to any 53 in
$IPF 180 allow udp from any to any 53 out
$IPF 185 allow tcp from any to any 53 out
$IPF 200 allow tcp from any to any 80 in
$IPF 210 allow tcp from any to any 80 out

# deny and log everything
$IPF 500 deny log all from any to any

Save and close the file.

kemudian lakukan perintah dibawah ini  

# sh /usr/local/etc/ipfw.rules

jika kurang jelas lihat di sini