Overview¶

UFW (Uncomplicated Firewall) is a user-friendly interface for managing firewall rules using iptables. It simplifies firewall configuration and is commonly used for:

Securing servers
Controlling network traffic
Restricting access to services
Basic cybersecurity defense

By default, UFW is disabled.

Installation¶

sudo apt-get install ufw

Explanation
Installs the UFW firewall package on the system.

Enable / Disable and Status¶

Enable UFW¶

sudo ufw enable

Explanation

Activates firewall
Applies rules
Enables at startup

Disable UFW¶

sudo ufw disable

Explanation
Stops firewall and disables it at startup.

Check Status¶

sudo ufw status

Verbose Status¶

sudo ufw status verbose

Explanation
Displays detailed information including default policies.

Numbered Rules¶

sudo ufw status numbered

Explanation
Shows rules with numbers for easy deletion.

Default Policies¶

Allow All Incoming Connections¶

sudo ufw default allow incoming

Deny All Incoming Connections (Recommended)¶

sudo ufw default deny incoming

Allow All Outgoing Connections¶

sudo ufw default allow outgoing

Deny All Outgoing Connections¶

sudo ufw default deny outgoing

Best Practice¶

sudo ufw default deny incoming
sudo ufw default allow outgoing

Explanation
Blocks unauthorized incoming traffic while allowing outbound connections.

Allow and Deny Rules¶

List Available Applications¶

sudo ufw app list

Allow a Service¶

sudo ufw allow ssh

Explanation
Allows SSH connections.

Deny a Service¶

sudo ufw deny ssh

Port-Based Rules¶

Allow Port¶

sudo ufw allow 80

Allow TCP Port¶

sudo ufw allow 80/tcp

Allow UDP Port¶

sudo ufw allow 80/udp

Deny Port¶

sudo ufw deny 80

Deny TCP/UDP Ports¶

sudo ufw deny 80/tcp
sudo ufw deny 80/udp

Advanced Rules¶

Allow from Specific IP¶

sudo ufw allow from 192.168.0.1

Allow from Subnet¶

sudo ufw allow from 192.168.0.0/24

Allow Specific IP to Specific Port¶

sudo ufw allow from 192.168.0.1 to any port 22

Allow with Protocol¶

sudo ufw allow from 192.168.0.1 to any port 22 proto tcp

Deny Rules¶

Same syntax applies using deny instead of allow.

Deleting and Resetting Rules¶

Delete Rule by Number¶

sudo ufw delete 1

Explanation
Deletes rule number 1 from the list.

Reset Firewall¶

sudo ufw reset

Explanation

Removes all rules
Resets to default state
Use carefully

Practical Examples¶

Secure Server Setup¶

sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow ssh
sudo ufw enable

Allow Web Traffic¶

sudo ufw allow 80
sudo ufw allow 443

Restrict SSH to Specific IP¶

sudo ufw allow from 192.168.1.10 to any port 22

Important Notes¶

Always allow SSH before enabling UFW to avoid lockout
Use numbered rules for easy management
Prefer restrictive rules (deny by default)
Test rules before deploying in production

Summary Table¶

Command	Purpose
`ufw enable`	Enable firewall
`ufw disable`	Disable firewall
`ufw status`	Check status
`ufw allow`	Allow traffic
`ufw deny`	Deny traffic
`ufw delete`	Remove rule
`ufw reset`	Reset firewall
`ufw default`	Set default policy

Conclusion¶

UFW is a powerful yet simple firewall tool that helps:

Secure Linux systems
Control incoming and outgoing traffic
Prevent unauthorized access

Mastering UFW is essential for system administrators and cybersecurity professionals to maintain a secure environment.