Options Used within iptables Commands https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/3/html/Reference_Guide/s1-iptables-options.html
How To Set Up a Firewall Using Iptables on Ubuntu 14.04 | DigitalOcean https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-using-iptables-on-ubuntu-14-04
How To Choose an Effective Firewall Policy to Secure your Servers | DigitalOcean https://www.digitalocean.com/community/tutorials/how-to-choose-an-effective-firewall-policy-to-secure-your-servers
How To List and Delete Iptables Firewall Rules | DigitalOcean https://www.digitalocean.com/community/tutorials/how-to-list-and-delete-iptables-firewall-rules
Minimal Iptables Configuration – Developer Should Know http://developer-should-know.tumblr.com/post/128018906292/minimal-iptables-configuration
How To Use RKHunter to Guard Against Rootkits on an Ubuntu VPS https://www.digitalocean.com/community/tutorials/how-to-use-rkhunter-to-guard-against-rootkits-on-an-ubuntu-vps