A Simple Linux Firewall – ufw

Configuring a firewall rule in Ubuntu typically involves using iptables or nftables. I have written a separate article on iptables here.

What if we wanted to make life a little less involved. The answer is ufw (Uncomplicated Firewall), which is a user-friendly front-end for managing iptables firewall rules.

Here’s how you can do it:

Step 1: Install UFW (if not already installed)

UFW usually comes pre-installed with Ubuntu. You can check this by entering:

sudo ufw status

If it’s not installed, you can install it by running:

sudo apt update
sudo apt install ufw

Step 2: Enable UFW

Before adding rules, make sure UFW is enabled:

sudo ufw enable

Step 3: Allow or Deny Specific Ports

You can allow or deny traffic through specific ports.

• Allow a Port: To allow incoming traffic on a specific port, use the following command: sudo ufw allow 22 Replace 22 with the port number you want to allow. For example, for HTTP traffic, you might allow port 80: sudo ufw allow 80
• Deny a Port: To deny traffic on a specific port, use: sudo ufw deny 22

Step 4: Allow or Deny Services by Name

You can also allow or deny services by name, such as ssh, http, or https.

• Allow a Service: sudo ufw allow ssh sudo ufw allow http
• Deny a Service: sudo ufw deny ssh

Step 5: Allow or Deny Traffic from Specific IP Addresses

You can control traffic from specific IP addresses.

• Allow an IP Address: sudo ufw allow from 192.168.1.100 This allows traffic from the IP 192.168.1.100 on all ports.
• Deny an IP Address: sudo ufw deny from 192.168.1.100

Step 6: Check the Status of UFW

To check the status and see the rules that are currently applied:

sudo ufw status

Step 7: Disable UFW (if needed)

If you need to disable the firewall for any reason, you can do so with:

sudo ufw disable

Step 8: Delete Rules

If you need to remove a rule, you can use:

sudo ufw delete allow 22

Replace allow 22 with the specific rule you want to delete.

Additional Tips

• Advanced Rules: UFW supports more complex rules, such as allowing/denying traffic to/from specific subnets, setting up logging, or configuring rate limits.
• Logging: To enable logging, use sudo ufw logging on.

This basic guide should help you configure most firewall rules on Ubuntu using UFW.

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