- pfSense: https://docs.netgate.com/pfsense/en/latest/
- iptables: https://wiki.nftables.org/wiki-nftables/index.php/Main_Page
- Cisco ASA: https://www.cisco.com/c/en/us/support/security/asa-5500-series-next-generation-firewalls/tsd-products-support-series-home.html
- Palo Alto NGFW: https://docs.paloaltonetworks.com/
- Stallings, W. Network Security Essentials
- Cheswick, W. R., Bellovin, S. M., & Rubin, A. D. Firewalls and Internet Security
- Cybrary: Firewall Fundamentals
- Udemy: Network Security and Firewalls