UFW Firewall Setup on Linux — Secure Your Server in 10 Minutes

UFW Firewall Setup on Linux

UFW (Uncomplicated Firewall) is the default firewall tool on Ubuntu and most Debian-based distros. It wraps iptables in a much simpler interface and is the fastest way to lock down a Linux server.

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Step 1 — Install UFW

UFW is pre-installed on most Ubuntu systems. Check if it's there:

sudo apt install ufw
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Step 2 — Check Current Status

sudo ufw status verbose
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If it says Status: inactive, UFW is installed but not yet enforcing rules.

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Step 3 — Set Default Policies

Before enabling, set your default behavior:

sudo ufw default deny incoming
sudo ufw default allow outgoing
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This blocks all inbound traffic by default and allows all outbound. You then open only what you need.

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Step 4 — Allow SSH (Critical — Do This Before Enabling)

If you're connected via SSH, allow it before enabling UFW or you'll lock yourself out:

sudo ufw allow ssh
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Or by port number:

sudo ufw allow 22/tcp
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If you use a non-standard SSH port (e.g., 2222):

sudo ufw allow 2222/tcp
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Step 5 — Allow Other Ports You Need

Web Server

sudo ufw allow 80/tcp    # HTTP
sudo ufw allow 443/tcp   # HTTPS
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Blockchain Nodes

sudo ufw allow 30303/tcp  # Ethereum P2P
sudo ufw allow 16110/tcp  # Kaspa RPC / P2P
sudo ufw allow 8333/tcp   # Bitcoin P2P
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Custom App Port

sudo ufw allow 8080/tcp
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Step 6 — Enable UFW

sudo ufw enable
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You'll be prompted to confirm. Type y and press Enter.

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Step 7 — Verify Your Rules

sudo ufw status numbered
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Example output:

Status: active

     To                         Action      From
     --                         ------      ----
[ 1] 22/tcp                     ALLOW IN    Anywhere
[ 2] 80/tcp                     ALLOW IN    Anywhere
[ 3] 443/tcp                    ALLOW IN    Anywhere
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Deleting Rules

Delete a rule by number (use status numbered to find the number):

sudo ufw delete 2
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Or delete by rule spec:

sudo ufw delete allow 80/tcp
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Disable UFW (If Needed)

sudo ufw disable
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This stops enforcement without deleting your rules.

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Rate Limiting (Brute Force Protection)

Limit connection attempts to SSH (blocks IPs that attempt 6+ connections in 30 seconds):

sudo ufw limit ssh
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Quick Reference

Goal	Command
Check status	sudo ufw status verbose
Default deny inbound	sudo ufw default deny incoming
Allow SSH	sudo ufw allow ssh
Allow port	sudo ufw allow 8080/tcp
Enable UFW	sudo ufw enable
Disable UFW	sudo ufw disable
Delete rule	sudo ufw delete [number]
Rate limit SSH	sudo ufw limit ssh

UFW is fast to configure and straightforward to maintain — every Linux server exposed to the internet should have it enabled.