## iptables
+ # so that firewall rules load at boot
+ apt-get install iptables-persistent
+ # edit rules
+ vim /etc/iptables/rules.v4
+ # reload rules
+ iptables-restore < /etc/iptables/rules.v4
+ # save rules
+ invoke-rc.d iptables-persistent save
+
+### Sample iptables firewall rules
+
+ root@server2:~# cat /etc/iptables/rules.v4
+ # Generated by iptables-save v1.4.21 on Wed Oct 14 22:17:08 2015
+ *filter
+ :INPUT ACCEPT [0:0]
+ :FORWARD ACCEPT [0:0]
+ :OUTPUT ACCEPT [72:34181]
+ -A INPUT -i lo -j ACCEPT
+ -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
+ -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
+ -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
+ -A INPUT -j DROP
+ COMMIT
+ # Completed on Wed Oct 14 22:17:08 2015
+ root@server2:~#
+
https://help.ubuntu.com/community/IptablesHowTo
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-using-iptables-on-ubuntu-14-04