Linux Firewall: Configuration, Tools, Best Practices & More

For modern organizations, safeguarding your system against cyber threats is paramount. Linux, renowned for its robust security features, offers a wide range of firewall solutions to strengthen your defenses. In this article, we will explore some of the top Linux firewall options, how to configure them, and the best strategies to use them effectively — helping you keep your systems and data secure.

Understanding Linux Firewalls

 

Linux Firewalls are the first line of defense against unauthorized access and malicious activities. They regulate incoming and outgoing network traffic based on predefined security rules. Two prominent firewall solutions in Linux are iptables and nftables. While iptables has been a staple for years, nftables is gaining traction for its enhanced performance and flexibility.

To gain a deeper understanding of these Linux firewalls solutions, let’s explore their configurations and functionalities.

 

An Overview of iptables & nftables

iptables has been the go-to firewall solution for Linux users for decades. It operates through a series of tables and chains, where packets are evaluated against predefined rules to determine their fate. These rules can be configured to permit, deny, or manipulate traffic based on various criteria, such as source IP, destination port, or protocol type.

nftables, the successor to iptables, introduces a more streamlined and efficient framework for packet filtering and manipulation. It offers a simplified syntax and improved performance, making it an attractive option for modern Linux distributions.

One key differentiator of nftables is its support for expressive rule sets, allowing for more granular control over network traffic. nftables has been gaining traction in recent versions of distributions due to its more recent, maintainable codebase. iptables’ code has been around for decades and was becoming too unmanageable for developers to improve upon.

To learn more about the differences between iptables and nftables.

How to Configure Your Linux Firewall with nftables

In this section, we will look at how you can configure a firewall in your Linux system using the nftables tool. With these steps, you can successfully establish a basic Linux firewall configuration to control incoming network traffic.

Step 1: Start and Enable nftables

In most Linux distributions, you will find nftables in the disabled state. So, at first, you will need to start it with systemctl and enable it to start on boot by running the following commands.

sudo systemctl start nftables
sudo systemctl enable nftables

Step 2: Create a Table

nftables uses tables to organize rules for different types of network traffic. A table acts as a container for chains and rules. Let’s create a table named my_firewall for general traffic filtering:

sudo nft add table inet my_firewall

inet specifies that this table handles both IPv4 and IPv6 traffic.

Other address families include ip, ip6, arp, bridge, and netdev.

Step 3: Create a Chain

Within the my_firewall table, we will create a chain named INPUT to control incoming traffic. A chain is a sequence of rules that are evaluated in order.

sudo nft add chain inet my_firewall INPUT { type filter hook input priority filter \; policy accept \; }

type filter hook input: This defines the chain as a filter for incoming traffic.

priority filter: Sets the priority of this chain.

policy accept: This is the default action. If no other rules match, traffic will be accepted.

Step 4: Add Rules to the Chain

Now let’s add some rules to the INPUT chain. A rule defines specific criteria for matching network traffic and specifies an action to take (e.g., accept, reject, drop).

Allow SSH (port 22):

sudo nft add rule inet my_firewall INPUT tcp dport 22 accept

Allow HTTPS (port 443):

sudo nft add rule inet my_firewall INPUT tcp dport 443 accept

Reject other incoming traffic:

sudo nft add rule inet my_firewall INPUT reject

Step 5: Verify Your Rules

To check the active rules, use the following command:

sudo nft list ruleset

This is a very basic example. You will likely need to add more specific rules based on your needs (e.g., allow specific IP addresses, deny certain protocols).

Linux Firewall Configuration: Our 5 Top Tips

Configuring a firewall on Linux can have a bit of a learning curve, but with the right approach, you can simplify the configuration process. Here are five practical tips that will help you streamline your firewall settings and improve your system security.

Tip 1: Start with a Simple Policy

Begin with a default deny-all policy and explicitly allow only what is necessary. However, before applying this rule, ensure your SSH connection is explicitly allowed to avoid locking yourself out of the system. This safeguards your access before blocking everything else. Using iptables or nftables to create default policies is easy, so make sure your ports are not leaked inadvertently.

Tip 2: Only Open Necessary Ports

Every open port counts as a potential entry point for attacks, so be cautious about which ports you leave open. You can restrict access to only the ports required for your applications or services, and close any that are not in use.

Tip 3: Use Zones or Chains for Organization

Organize your firewall rules with zones (firewalld) or chains (iptables, nftables). This lets you apply different rules based on network interfaces or trust levels. Structured rules make configurations easier to manage and reduce the chance of errors.

Tip 4: Regularly Review and Test Rules

Firewall rules should not be “set and forget.” Periodically review them to ensure they meet current requirements. After any change, test thoroughly to confirm your rules function as intended without accidentally blocking legitimate traffic.

Tip 5: Keep Your Firewall Software Up to Date

Stay on top of updates for firewall tools you use like nftables, ufw, or firewalld. Updates often include patches for security vulnerabilities, which are essential for maintaining effective firewall protection.

Find out more about TuxCare’s live patching services.

How to Troubleshoot Firewall Configuration Issues

Firewall configuration issues can disrupt your connections and leave services inaccessible. Here’s how to troubleshoot them:

Check Firewall Status: Use commands like firewalld-cmd --state, iptables -L, or ufw status to check the current status of your firewall.

Review Active Rules: Carefully examine current rules to ensure they match with your intended traffic policies. Misconfigured rules are a common source of problems.

Test Network Connectivity: Use tools like ping, traceroute, or telnet to test connectivity to both internal and external resources. This helps pinpoint blocked traffic.

Examine Firewall Logs: Check firewall logs for error messages or dropped packets to understand what might be causing disruptions.

Temporarily Disable the Firewall: Temporarily disable the firewall to confirm if it is the source of the problem.

Our 10 Recommended Linux Firewall Solutions in 2025

There are tons of options out there, from simple tools for beginners to advanced firewall solutions. We have put together a list of ten of the best firewalls you will find in 2025, whether you like things straightforward or need robust, feature-rich protection.

1. iptables

iptables has been a workhorse in Linux networking for ages. It gives you fine control over network traffic with its rule-based system, which is why expert users often liked it. Though now considered legacy software and largely replaced by nftables, it is still relevant and widely used for managing Linux firewalls in Linux.

Key Features:

• Granular rule chains for precise traffic management.
• Extensive documentation and community support (though less active today).
• Best suited for backward compatibility on older Linux systems.

Availability:

Pre-installed on many older Linux distributions.

2. nftables

Nftables is the new standard in Linux firewall which replaces old iptables with a cleaner syntax, better performance, and improved IPv4/IPv6 support. It is designed to be easier to configure, run faster, and fix some of the problems iptables had.

Key Features:

• Handles IPv4 and IPv6 easily; you don’t have to write separate rules for each.
• Supports hardware acceleration for better performance.
• Simplified syntax reduces configuration errors.

Availability:

Open source; typically included in standard Linux repositories.

3. Firewalld

Firewalld provides a simpler and user-friendly interface for firewall management. Built on nftables, it takes the complexity out of managing nftables (or iptables on older systems) by using “zones.” Each zone has its own set of rules, so it’s easy to manage different network connections. It is especially suited for users needing quick and easy setup without manually writing nftables rules. Firewalld is the default firewall in RHEL 7 and later versions, as well as in popular RHEL-based distributions like CentOS, AlmaLinux, and Fedora.

Key Features:

• Zone-based rule management simplifies configuration for different interfaces.
• Dynamic updates eliminate the need for service restarts.
• GUI integration (e.g., Cockpit) makes it accessible to beginners.

Availability:

Open source; typically included in standard Linux repositories.

4. UFW (Uncomplicated Firewall)

UFW is all about simplicity. Its command-line syntax makes rule configuration straightforward. It is also the default firewall tool on Ubuntu-based distributions.

Key Features:

• The commands are easy to remember and use, even if you’re new to firewalls.
• Pre-built profiles simplify setup for common services.
• Ideal for small-scale or personal projects.

Availability:

Open source; typically included in standard Linux repositories.

5. CSF (ConfigServer Security & Firewall)

CSF provides additional security features, like intrusion detection and login failure tracking. It is widely used in web hosting environments, integrating seamlessly with cPanel. CSF is well-suited for administrators who need detailed security management for servers.

Key Features:

• Includes login failure detection for improved access control.
• Real-time alerts keep administrators informed of threats.
• Stateful packet inspection ensures comprehensive traffic analysis.

Availability:

Free download from the official ConfigServer website.

6. Shorewall

Shorewall uses configuration files to simplify the management of complex firewall rules, making it a favorite among administrators handling multi-zone setups.

Key Features:

• Zone-based architecture for precise traffic control.
• Detailed logging aids in troubleshooting.
• Robust IPv6 and NAT rule support for modern networks.

Availability:

Available through most Linux distribution repositories.

7. IPFire

IPFire is an open-source firewall solution offering enhanced Linux security, intrusion prevention, and VPN support. It’s designed as a standalone distribution, making it an excellent choice for dedicated firewall hardware or secure gateways.

Key Features:

• Built-in intrusion detection to monitor threats.
• Web interface for easy administration.
• Integrated VPN support enhances remote security.

Availability:

Downloadable as an ISO image from the IPFire website.

8. pfSense

While pfSense is FreeBSD-based, it can run in a virtual machine on Linux, offering enterprise-grade firewall and routing capabilities.

Key Features:

• User-friendly web interface with advanced visual tools.
• Supports VPN, load balancing, and failover setups.

Availability:

Free with optional paid support from Netgate.

9. OpenWRT

OpenWRT is a Linux-based firewall and router solution for embedded devices. It’s highly customizable, making it suitable for managing home networks or IoT devices. It includes tools for traffic monitoring and robust firewall capabilities.

Key Features:

• Extensive package library for tailored setups.
• Traffic shaping, monitoring, and QoS tools included.
• Ideal for users managing router firmware.

Availability:

Free download from the OpenWrt website.

10. VyOS

VyOS, a network OS built on a Linux fork, delivers advanced routing and firewall features. It is suitable for large-scale or complex network environments.

Key Features:

• Powerful CLI for precise control over configurations.
• Supports dynamic routing protocols like BGP and OSPF.
• Enterprise-grade reliability with frequent updates.

Availability:

Free and open-source version available with paid enterprise support.

 

Best Practices for Effective Linux Firewalls Management

 

Regardless of the Linux Firewalls solution chosen, certain best practices can maximize its effectiveness in safeguarding your system:

 

1. Regular Rule Audits: Periodically review and update firewall rules to adapt to evolving security threats and system requirements.
2. Implement Default Deny Policies: Adopt a default deny policy for inbound and outbound traffic to minimize the attack surface.
3. Use Application-Level Filtering: Leverage application-level filtering to enforce security policies based on specific software or services.
4. Enable Logging and Monitoring: Enable logging to track network traffic and detect potential security incidents. Regularly monitor firewall logs for anomalies and suspicious activities.
5. Implement Intrusion Detection Systems (IDS): Supplement firewall defenses with intrusion detection systems to identify and respond to malicious activities in real time.
6. Employ Network Segmentation: Segmenting networks into distinct zones can contain breaches and limit the impact of security incidents.

Final Thoughts

 

Linux firewalls play a crucial role in safeguarding your system against cyber threats. By understanding the nuances of firewall solutions like iptables and nftables and adopting best practices for effective firewall management, you can enhance the security posture of your Linux environment.

Remember, security is a continuous process, and staying vigilant is key to mitigating risks and protecting your valuable assets in the ever-evolving threat landscape. With the right tools and strategies, you can fortify your defenses and ensure the integrity and confidentiality of your system and data.