Now since we have already studied about Linux Firewall using IPtables, let’s dive into another commonly used firewall i.e., UFW Firewall also called as Uncomplicated Firewall.
Table of Contents
- Introduction to UFW
- Why Use UFW Instead of IPTables?
- UFW Internals and Backend
- Basic UFW Commands
- Default Policies: What Happens When Nothing Matches
- Allowing and Denying Services
- Allow/Deny by IP Address
- Port Ranges, Protocols, and Advanced Matches
- UFW with Applications (App Profiles)
- Logging and Monitoring Traffic
- GUI for UFW: Gufw
- Persistent Rules and System Boot
- Common Troubleshooting
- Conclusion
1. Introduction to UFW Firewall
UFW (Uncomplicated Firewall) is a simplified frontend for managing IPTables on Linux systems. It was developed by Canonical to make firewall configuration more intuitive, especially for beginners.
UFW is ideal for:
- Desktop users
- Basic and intermediate server users
- Anyone who prefers readable commands over complex IPTables syntax
2. Why Use UFW Instead of IPTables?
| Feature | IPTables | UFW |
|---|---|---|
| Complexity | Steep learning curve | Beginner-friendly |
| Configuration | Detailed & granular | Human-readable |
| Use case | Advanced setups | General security needs |
| Backend | Native | Uses IPTables behind the scenes |
3. UFW Internals and Backend
- UFW operates on top of iptables/netfilter.
- UFW rules are stored in /etc/ufw/ (e.g., before.rules, user.rules).
- UFW configuration file: /etc/default/ufw
- On Ubuntu systems, it integrates well with Debian networking and cloud-init.
4. Basic UFW Commands
Enable UFW:
sudo ufw enable
Disable UFW:
sudo ufw disable
Check UFW status:
sudo ufw status
More detailed:
sudo ufw status verbose
Reset all rules:
sudo ufw reset
5. Default Policies
Before adding rules, set default policies:
sudo ufw default deny incoming
sudo ufw default allow outgoing
This blocks all incoming traffic except what is explicitly allowed.
6. Allowing and Denying Services
Allow incoming SSH:
sudo ufw allow ssh
# or
sudo ufw allow 22/tcp
Deny HTTP:
sudo ufw deny 80
Allow HTTPS only:
sudo ufw allow 443/tcp
Specify port and protocol:
sudo ufw allow 53/udp
7. Allow/Deny by IP Address
Allow all traffic from a specific IP:
sudo ufw allow from 192.168.1.100
Allow from IP to specific port:
sudo ufw allow from 192.168.1.100 to any port 22
Block specific IP:
sudo ufw deny from 203.0.113.5
8. Port Ranges, Protocols, and Advanced Matches
Allow a port range:
sudo ufw allow 1000:2000/tcp
Allow specific protocol:
sudo ufw allow proto udp from any to any port 1194
Use interfaces:
sudo ufw allow in on eth0 to any port 3306
9. UFW with Applications (App Profiles)
UFW can read application profiles stored in:
/etc/ufw/applications.d/
List available profiles:
sudo ufw app list
Example:
sudo ufw allow 'Apache Full'
To view details:
sudo ufw app info 'Apache Full'
10. Logging and Monitoring Traffic
Enable logging:
sudo ufw logging on
Disable logging:
sudo ufw logging off
Log levels:
- off
- low (default)
- medium
- high
- full
Change log level:
sudo ufw logging medium
Logs are stored in /var/log/ufw.log
11. GUI for UFW: Gufw
Gufw is a graphical frontend for UFW.
Install on Ubuntu:
sudo apt install gufw
Features:
- Easy toggling of firewall state
- Quick add/remove rules
- Good for desktop users unfamiliar with terminal
12. Persistent Rules and System Boot
UFW rules are persistent across reboots once enabled. No additional steps are required.
To confirm:
sudo systemctl status ufw
To enable at boot:
sudo systemctl enable ufw
13. Common Troubleshooting
Check if UFW is active:
sudo ufw status
Rule not working?
- Check ordering: ufw processes rules in the order defined
- Make sure the rule is for the correct interface/protocol
- Check if another firewall (like firewalld or nftables) is active
Reset and start fresh:
sudo ufw reset
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow ssh
sudo ufw enable
14. Conclusion
UFW is the perfect firewall utility for Linux users who want simple, readable, and effective security without the complexity of raw IPTables syntax. It’s especially great for:
- System administrators who want quick rule management
- Users of Ubuntu or Debian-based systems
- Developers securing test environments or cloud instances
Key Benefits:
✅ Easy to learn
✅ Uses readable syntax
✅ Backend power of IPTables
✅ Automatically persistent
By learning UFW, you gain the confidence to manage Linux firewall rules securely and efficiently — even in production environments.