SANS firewall checklist is available here.
Firewalls are becoming increasingly important in today’s world. Hackers and automated scripts are constantly trying to invade your system and use it for Bitcoin mining, botnets or other things. To prevent these attacks, you can use a firewall on your system. IPTables is the strongest firewall in Linux because it can filter packets in the kernel before they reach the application. Using IPTables is not very easy for Linux beginners. We have created easywall - the simple IPTables web interface . The focus of the software is on easy installation and use. Access this neat software over on github: easywall