How to Set Up a Firewall on Raspberry Pi (Easy & Secure) - Raspberry Pi BD

This guide walks you through setting up a basic firewall on Raspberry Pi using UFW (Uncomplicated Firewall) or iptables.

🛡 Why Use a Firewall on Raspberry Pi?

• Block unwanted traffic
• Allow only specific ports
• Prevent unauthorized access to services
• Strengthen your Raspberry Pi’s security posture

🧰 What You’ll Need

• Raspberry Pi running Raspberry Pi OS
• Terminal or SSH access
• Basic Linux knowledge

⚙️ Method 1: Using UFW (Uncomplicated Firewall)

Step 1: Install UFW

sudo apt update
sudo apt install ufw

Step 2: Set Default Rules

sudo ufw default deny incoming
sudo ufw default allow outgoing

Step 3: Allow SSH (important!)

sudo ufw allow ssh

Step 4: Enable UFW

sudo ufw enable

Step 5: Check Status

sudo ufw status verbose

⚙️ Method 2: Using iptables

iptables gives you more control but requires deeper networking knowledge. Here’s a basic example:

Step 1: Drop All Incoming by Default

sudo iptables -P INPUT DROP
sudo iptables -P FORWARD DROP
sudo iptables -P OUTPUT ACCEPT

Step 2: Allow Loopback and SSH

sudo iptables -A INPUT -i lo -j ACCEPT
sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT

Step 3: Save the Rules

sudo apt install iptables-persistent
sudo netfilter-persistent save

🔁 How to Reset Firewall Rules

To reset UFW:

sudo ufw reset

To flush iptables:

sudo iptables -F

🧠 Pro Tips

• Always allow SSH before enabling the firewall, or you may lock yourself out
• Use sudo ufw allow [port] to open access to specific services (like HTTP or VNC)
• Run a port scan from another machine to check which ports are open