8 Best Open Source Firewalls to Protect Your Network in 2023

Protecting your network infrastructure from cyber attacks is crucial in today‘s threat landscape. While commercial firewall solutions can be expensive, open source firewalls offer a compelling free alternative without compromising on features.

As a cybersecurity professional and open source enthusiast, I evaluated some of the top open source firewalls based on critical factors like security, scalability, ease of use and community support. Here are my top recommendations:

Why Open Source Firewalls?

Before jumping into the firewall reviews, let‘s first understand what open source firewalls are and their benefits:

  • No licensing cost – You can use them free of charge
  • Customization – Their open source code can be customized as per your needs
  • Community support – Developers and users contribute to fixes and new features
  • Transparency – You can audit the source code for security issues

Of course, the downside is that open source projects rely on community support and may lack formal vendor backing. But their passionate user base makes up for this limitation.

Now let‘s explore some of the best open source firewalls available today:

Evaluation Criteria for Best Firewalls

I evaluated firewalls on the following key parameters important for enterprise use:

Security Features – IPS/IDS, antivirus integration, VPN, deception tools etc.

Ease of Use – Intuitive interfaces and workflows for setup, management & monitoring

Scalability & High Availability – Ability to handle large traffic volumes without downtime

Deployment Options – Software, hardware, virtual appliances, cloud instances etc.

Community Support – Responsiveness on forums, regular updates and security fixes

With these criteria in mind, here are the firewalls that delivered best-in-class capabilities:

1. pfSense

pfSense is perhaps the most popular open source firewall and routing software solution. It is based on FreeBSD OS and offers an extensive range of networking features beyond just a firewall.

Key Highlights

  • Advanced firewall rules with stateful packet inspection
  • IDS/IPS and threat detection with packages like Snort
  • Web proxy and traffic shaping for QoS
  • OpenVPN and IPsec VPN connectivity
  • Load balancing for high availability across multiple WAN links

pfSense has a solid community backing, a user-friendly web interface, and adds new features/fixes regularly. You can deploy it as a virtual machine, hardware appliance, or cloud instance.

It scales well to meet the needs of small offices to large enterprises. The built-in package manager allows further customization with 100+ third-party packages – giving it an app store like capability!

Use Cases

  • Secure corporate VPN gateway
  • Multi-WAN routers with load balancing
  • Inter-office secure connectivity over IPSec
  • Threat monitoring, analysis and prevention

Despite its many strengths, pfSense lacks native anti-virus scanning and application-layer filtering capabilities. But its package system allows integration of these via community plugins.

Overall, pfSense remains my first choice for most firewall deployments. It just has too many features to ignore given its free usage.

Helpful Resources

2. IPFire

IPFire is another Linux-based open source firewall optimized for small network deployments. It comes with a hardened kernel and minimal footprint that enhances security while using fewer resources.

Some notable aspects:

Key Highlights

  • Intrusion prevention via anomaly detection
  • Real-time performance monitoring
  • Easy setup wizard for quick installations
  • Role-based access control for admins
  • Optional Guardian add-on for automated threat response

IPFire keeps things simple yet effective for SOHO segments, unlike pfSense‘s enterprise-class capabilities. The small size and modular architecture make IPFire suitable for basic routing, VPN, proxy or VoIP uses cases as well.

It may not scale to match pfSense‘s mammoth proportions but offers a handy network security toolkit nonetheless. And the intelligent IDS is surprisingly accurate in detecting malware and network anomalies.

Helpful Resources

3. OPNSense

OPNSense started as a fork of the pfSense project before taking its own development direction. As such, it inherits the solid FreeBSD foundation and many networking capabilities of pfSense itself.

Let‘s glance at some noteworthy aspects:

Key Highlights

  • Traffic analysis via netflow protocol
  • Intrusion detection plugins
  • Captive portal for access control
  • Forward caching HTTP proxy
  • High availability with carp protocol failover

OPNSense additionally brings UI translations to many European and Asian languages – something I missed in pfSense. This better localization coupled with its feature set makes OPNSense a competent open source firewall solution.

It also seems more receptive to user feedback for enhancements compared to pfSense‘s closed development model nowadays. So keep an eye on OPNSense as it races to bridge the gap.

Helpful Resources

4. Smoothwall Express

Smoothwall Express is designed specifically as an easy-to-use firewall for novice users and smaller networks. Don‘t be fooled by its simple looks though – it packs quite a punch for blocking threats and unauthorized access attempts.

Key Highlights

  • Web-based user interface for configuration
  • External, internal and DMZ firewalling
  • Integrated web proxy for caching and filtering
  • Bandwidth monitoring
  • Live traffic statistics

I especially liked Smoothwall‘s web proxy which accelerates web traffic while blocking access to unwanted sites – acting as a basic secure web gateway.

Of course, power users may find the interface limiting. But Smoothwall Express works great for basic network deployments like cafes, retail stores or home use. Did I mention it‘s completely free without any strings attached?

Helpful Resources

5. ufw – Uncomplicated Firewall

Most network security guides for Linux distros recommend ufw (uncomplicated firewall) for host-based firewalling. As the name suggests, ufw offers simple yet effective firewall management from the command line.

Key Highlights

  • Rule-based interface for allowing or blocking traffic
  • Support for common Linux services out of the box
  • Integration with iptables for packet filtering
  • Port forwarding capabilities

So while ufw excels for instance-level security groups, it does not provide advanced logic for enterprise traffic filtering. Think of it like a basic building block that you can combine with other tools like Snort.

I recommend ufw for safeguarding Linux servers, Docker hosts, and related single node deployments. It is fast, widely supported and gets the firewalling basics right.

Helpful Resources

6. CSF – ConfigServer Security Firewall

The ConfigServer Security firewall takes server hardening to the next level for Linux. Its stateful packet inspection filters unauthorized traffic while also securing the host itself.

Key Highlights

  • Testing suite to identify system vulnerabilities
  • Rootkit detection
  • Advanced blocking of web exploits and DDOS
  • Jailshell for isolating suspicious users
  • Firewall driven by policies instead of rules

The application-layer defenses make csf very effective against XSS, SQLi or other attacks on web services. So it‘s found in many hosting environments to isolate website risks.

While the syntax does have a learning curve, the developer community is very responsive to guide new users. Just don‘t expect a pretty UI!

Helpful Resources

7. Endian Firewall Community

This aptly named firewall distro brings together open source security tools like Snort, Squid, Suricata, and Pfring into a single engine – drastically reducing deployment effort.

The easy yet feature-rich Endian firewall is a good fit for small offices, hotels, cyber cafes – anywhere that needs WiFi security, web filtering, VPN access in one package.

Key Highlights

  • Hardened OS optimized for security
  • Web control via blacklists
  • Site-to-site VPN and remote access
  • Intrusion prevention module
  • Bandwidth monitoring and QoS

I liked how Endian firewall simplifies typically complex elements like firewall rulesets, VPN connections, proxies etc. via its intuitive interface. This makes secure networking accessible for non-expert admins as well.

The commercial version adds premium support, a central management console and other enterprise-friendly capabilities. But even the free community edition is feature rich for most SMB scenarios.

Helpful Resources

Bonus: Firewall Terminology

If you are new to network security, here is a quick primer on common firewall concepts:

  • DMZ – Demilitarized zone for hosting publicly exposed services like mail servers in isolation.
  • Port forwarding – Forwards incoming traffic from firewall‘s port to a specific IP and port on private network.
  • MAC filtering – Allow or block network access based on device MAC addresses.
  • Stateful inspection – Firewall remembers context of connections to allow return traffic automatically.
  • Zones – Logical segregation of traffic into subnets – public, private, DMZ etc.

Getting familiar with these firewall basics will help you better leverage their capabilities. You can refer to detailed network security tutorials for more concepts.

Summing it Up

This concludes my guide on top open source firewalls for better network protection. Here is a quick summary of recommendations:


  • pfSense – Most comprehensive open source firewall

Also Great

  • IPFire – Simple yet powerful protection
  • OPNSense – Promising pfSense alternative
  • Smoothwall – User-friendly basic firewall

I suggest matching firewall capabilities like VPN, proxies etc. to your actual business needs. An open source model gives the flexibility to plugin required modules as you scale.

A defense in depth approach with multiple overlapping security layers is always wise for critical infrastructure. So utilize firewalls, IPS, malware scanning, host hardening and other such tools together to thwart advanced persistent threats.

I hope this guide helps identify the right open source firewall for your next network deployment. Share your feedback or questions via comments.