Iptables firewall on Debian | MyLiteratureTechLife.COM

 iptables -L

 Chain INPUT (policy ACCEPT)
 target     prot opt source               destination
 
 Chain FORWARD (policy ACCEPT)
 target     prot opt source               destination
 
 Chain OUTPUT (policy ACCEPT)
 target     prot opt source               destination

nano -w /etc/iptables.test.rules

*filter
 
 # Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
 -A INPUT -i lo -j ACCEPT
 -A INPUT -i ! lo -d 127.0.0.0/8 -j REJECT
 
 # Accepts all established inbound connections
 -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
 
 # Allows all outbound traffic
 # You could modify this to only allow certain traffic
 -A OUTPUT -j ACCEPT
 
 # Allows HTTP and HTTPS connections from anywhere (the normal ports for websites)
 -A INPUT -p tcp --dport 80 -j ACCEPT
 -A INPUT -p tcp --dport 443 -j ACCEPT
 
 # Allows SSH connections for script kiddies
 # THE -dport NUMBER IS THE SAME ONE YOU SET UP IN THE SSHD_CONFIG FILE
 -A INPUT -p tcp -m state --state NEW --dport 30000 -j ACCEPT
 
 # Now you should read up on iptables rules and consider whether ssh access
 # for everyone is really desired. Most likely you will only allow access from certain IPs.
 
 # Allow ping
 -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
 
 # log iptables denied calls (access via 'dmesg' command)
 -A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7
 
 # Reject all other inbound - default deny unless explicitly allowed policy:
 -A INPUT -j REJECT
 -A FORWARD -j REJECT
 
 COMMIT

iptables-restore < /etc/iptables.test.rules

iptables -L

iptables-save > /etc/iptables.up.rules

 nano -w /etc/network/if-pre-up.d/iptables

#!/bin/bash
 /sbin/iptables-restore < /etc/iptables.up.rules

chmod +x /etc/network/if-pre-up.d/iptables