Linux(Application Security): Steps to open all incoming connections and block all incoming connections

Lets say, We want to open all incoming connections to Nginx’s port(8095) and block all incoming connections to Apache’s port(8085). Also make sure rules are permanent.

Step 1:

Flush the current iptables rules

iptables -F

Step 2:

Allow incoming traffic on Nginx’s port (8095)

iptables -A INPUT -p tcp --dport 8095 -j ACCEPT

Step 3:

Block incoming traffic on Apache’s port (8085)

iptables -A INPUT -p tcp --dport 8085 -j DROP

Step 4:

Save the changes to the iptables rules

iptables-save > /etc/sysconfig/iptables

Step 5:

Restart the iptables service to apply the changes

systemctl restart iptables

With these steps, incoming connections to Nginx’s port 8095 will be allowed and incoming connections to Apache’s port 8085 will be blocked. To make the rules permanent, you need to add the iptables-save command in the appropriate script that runs at boot time.