A firewall is a security mechanism that controls incoming and outgoing network traffic based on predefined rules. Its purpose is to block unauthorized access while allowing legitimate connections.
On Linux servers, firewall configuration is a critical security layer that operates at the network level.
Linux processes network traffic through the netfilter framework at the kernel level. Firewall tools interact with this framework to decide how packets are handled.
Each packet is evaluated with one of the following actions:
Iptables is a long-established low-level firewall management tool in Linux. It controls traffic using chains and rules.
Iptables is powerful and flexible, but can be complex to manage.
UFW (Uncomplicated Firewall) is a simplified firewall tool built on top of iptables.
It is commonly used on Ubuntu-based systems to quickly implement essential firewall rules.
ufw enable ufw allow ssh ufw allow 80 ufw allow 443 ufw status
A server without a firewall is directly exposed to the internet and vulnerable to automated attacks.
From a knowledge base perspective, firewall configuration is the first line of defense in server security.
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