Background: https://www.freepbx.org/a-secure-freepbx-is-a-happy-freepbx/

Pro Tips Video: https://www.youtube.com/watch?v=CD_k5PrY7Xc

Setup Guide: https://www.freepbxhosting.com/comprehensive-freepbx-firewall-setup-guide/

Basic Firewall Configuration - Watch First: https://youtu.be/CD_k5PrY7Xc

Run the Firewall Wizard:

FreePBX → Connectivity → Firewall → Settings (tab) → Re-Run Wizard

• Whitelist Host? → Yes
• Whitelist Network? → No
• Enable Responsive Firewall? → Yes
• Automatically configure Asterisk IP Settings? → Yes

FreePBX → Connectivity → Firewall → Networks (tab)

This tab overrides the default permission for an interface.

• Trusted → Only add trusted admin IP, network or FQDN
• Local → Add IP, network or FQDN for normal voice traffic (where phones are)

FreePBX → Connectivity → Firewall → Interfaces (tab)

This tab sets the Default Traffic Zones.

• You must set at least one interface as Internet
• Single-interface systems will be set as Internet (eth0)
• Trusted means no filtering at all

FreePBX → Connectivity → Firewall → Responsive Firewall (tab)

• Enable for any protocol in use
• This will open ports for limited access
• Too many failures will result in that IP being blocked

FreePBX → Connectivity → Firewall → Intrusion Detection (tab)

• Shows blocked IPs
• You can whitelist IPs or networks

-A INPUT -p udp -m multiport --dports 5060,5061 -m set --match-set fail2ban-ASTERISK src -j REJECT --reject-with icmp-port-unreachable
-A INPUT -p tcp -m multiport --dports 5060,5061 -m set --match-set fail2ban-ASTERISK src -j REJECT --reject-with icmp-port-unreachable
-A INPUT -p tcp -m multiport --dports 22 -j fail2ban-ssh
-A INPUT -m set --match-set voip_bl src -j DROP
-A INPUT -i lo -j ACCEPT
-A INPUT -p udp -m udp --dport 10000:20000 -j ACCEPT
-A INPUT -p udp -m udp --dport 2727 -j ACCEPT
-A INPUT -p udp -m udp --dport 4569 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p udp -m udp --dport 5060:5061 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 5060:5061 -j ACCEPT
-A INPUT -s known_external_proxy -p udp -m udp --dport 5060:5061 -j ACCEPT
-A INPUT -p udp -m udp --dport 5060:5061 -m string --string "User-Agent: VaxSIPUserAgent" --algo bm --to 65535 -j DROP
-A INPUT -p udp -m udp --dport 5060:5061 -m string --string "User-Agent: friendly-scanner" --algo bm --to 65535 -j REJECT --reject-with icmp-port-unreachable
-A INPUT -p udp -m udp --dport 5060:5061 -m string --string "REGISTER sip:" --algo bm --to 65535 -m recent --set --name VOIP --mask 255.255.255.255 --rsource
-A INPUT -p udp -m udp --dport 5060:5061 -m string --string "REGISTER sip:" --algo bm --to 65535 -m recent --update --seconds 60 --hitcount 12 --rttl --name VOIP --mask 255.255.255.255 --rsource -j DROP
-A INPUT -p udp -m udp --dport 5060:5061 -m string --string "INVITE sip:" --algo bm --to 65535 -m recent --set --name VOIPINV --mask 255.255.255.255 --rsource
-A INPUT -p udp -m udp --dport 5060:5061 -m string --string "INVITE sip:" --algo bm --to 65535 -m recent --update --seconds 60 --hitcount 12 --rttl --name VOIPINV --mask 255.255.255.255 --rsource -j DROP
-A INPUT -p tcp -m tcp --dport 5060:5061 -m hashlimit --hashlimit-upto 6/sec --hashlimit-burst 5 --hashlimit-mode srcip,dstport --hashlimit-name tunnel_limit -j ACCEPT
-A INPUT -p udp -m udp --dport 5060:5061 -m hashlimit --hashlimit-upto 6/sec --hashlimit-burst 5 --hashlimit-mode srcip,dstport --hashlimit-name tunnel_limit -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p icmp -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 137 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 138 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 139 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 445 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 10000 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 123 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p udp -m udp --dport 123 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 5038 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 58080 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 55050 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p tcp -m tcp --dport 514 -j ACCEPT
-A INPUT -s xxx.xxx.xxx.xxx/24 -p udp -m udp --dport 514 -j ACCEPT
-A INPUT -j DROP
-A OUTPUT -j ACCEPT