A firewall is a set of parameters put in place both on hardware and software to help protect our systems from hackers, snoopers, phishing, DDOs attacks, etc.

from gaining access to our systems through the network. For startups and small businesses, it is economical for them to adopt open-source firewalls to cut down costs and improve their ROI.

Down below is a list of the 15 best open-source firewalls I recommend for small businesses and startups, as there are a bunch of open-source firewalls that could get you spoiled for choice.

Err no more, I’m here to shed some light and guide you through the firewalls available to date under the MIT license for you. Thanks for your patience!

1. PFSence

PFSense is an open-source software distribution based on FreeBSD, suitable as both a firewall and a router.

It is highly customizable and added functionalities are viable with no compromise on security features on it. The best open-source firewall so far, in my opinion, don’t hesitate to go for it because PFSense is worth it! Highly recommended!

2. ClearOSFirewall

ClearOSFirewall is control-based open-source firewall that converts your PC to a dedicated firewall and internet gateway.

Open-source Firewalls clear OS

This ClearOSFirewall comes in three editions, for business, home, and community. One most fascinating thing about the community edition is that it is free for life.

The ability to extend its functionality by installing additional apps is fascinating. It is highly recommended for small businesses and startups.

3. Endian Firewall Community (EFC)

EFC is a Linux based open-source firewall security software which turns unused part of your computer hardware resource into a complete firewall solution to turn away potential network threats.

Open-source Firewalls  Endian Firewall Community (EFC)

EFC covers a variety of security tasks including stateful packet firewalls, web and email security, anti-virus and VPN (IPsec & SSL). Still, I can say EFC is highly recommended for SMBs.

4. IPFire

IPfire is also a Linux-based open-source distribution with flexible and modular characteristics. It can be deployed as a firewall, proxy server or VPN gateway.

Open-source Firewalls IPFire

Interestingly, it has a custom package called Pakfire that can be extended with add-ons.

5. NetDeep Secure

NetDeep Secure is another open-source firewall with plenty of secure offers from application firewall; Rules by Zone(internet, Wi-Fi, DM2), Deep Packet Inspection (DPI) web proxy, URL filter, local authentication, Radius, LD AP, we b access policies by groups, navigation reports, Dynamic DNS, DHCP server, captive portal and Wi-Fi management, monitoring dashboard, safe search, SNMP, SSL VPN, IPsec VPN, real-time bandwidth and consumption monitor.

Open-source Firewalls

Still, I would say it is recommended for SMBs.

6. VyOS

VyOs is a Linux based open-source network OS with multiple applications such as Quagga, ISC DHCPD, OpenVPN, strong S/WAM and many other features brought under one management interface.

It can be install on both physical and virtual machine or even cloud platform. It is similar to traditional hardware routers but uses a command-line interface to manage it.

7. SmoothWall

SmoothWall is a free open-source firewall solution that uses its own security-hardened Linux OS.

Open-source Firewalls

It is a good open-source security system that can be operated using a web interface.

8. Shorewall

The shorewall is a gateway/firewall configuration tool for GNU/Linux.

Shorewall has the easiest IPtable configuration tools which are very powerful and flexible.

9. LineWize

LineWize is a cloud-managed open-source firewall for education purposes. It is basically designed for schools and colleges.

Open-source Firewalls

Even though you may get maximum usage of the free package, still you could miss out on the premium privileges that come with subscriptions.

Its cloud features include; cloud management, real-time traffic reporting, snapshot configuration, bandwidth control, easy VPN provisioning, enterprise-grade firewall, layer 7 filtering and analytics, and identity management.

10. Untangle

It is free software that is flexible and interactive. It comes with different software modules that can be enabled or disabled according to the user requirement.

Its core features include; virus Blocker, firewall, web monitor, spam blocker lite, ad blocker, OpenVPN, captive portal, intrusion prevention, phish blocker and many more.

11. OPNSense

OPNSense is an open-source, easy-to-use and easy-to-build FreeBSD based firewall and routing platform. It is bundled with among others the best features available on commercial firewalls.

Open-source Firewalls

The core features of the OPNSense include; traffic shaper, captive portal, forward caching proxy, VPN, high availability and hardware failover, intrusion detection and inline prevention, reporting and monitoring tools, support for the plugin, DNS and DHCP server and relay.

12. Tiny Wall

This is yet another free firewall that protects without displaying notifications and prompts synonymous with most firewalls.

It comes with an application scanner that scans programs on your computer and adds them to a safe list.

The connection monitor shows all active processes with an internet connection and the user is at liberty to terminate a process or send it to an online virus scanner.

13. GlassWire

If you’re looking for a firewall with a pretty simple user interface; GlassWire is your stop shop.

Open-source Firewalls

It has five tabs with specific functionality. Firewall tab shows actively running program, the usage tab displays how much data each app used over a period, network tab receives alerts when the new devices join the network.

One more fascinating feature about GlassWire is the incognito mode that prevents traffic unless turned on, and the ability to snooze notifications is breathtaking.

14. PeerBlock

PeerBlock blocks the listed IP addresses under a certain category from accessing the network resource as well as prevents us from accessing theirs.

You can make a list of IP addresses to be denied access, interestingly; you can update the list anytime at your convenience.

15. AVS Firewall

To wrap up the list of the best 15 open-source firewalls is AVS Firewall. It has a friendly user interface, while protection from malicious registry changes is guaranteed.

It also blocks pop-up windows, flash banners, and ads. Parent control allows access to an explicit list of websites and can be password protected to prevent unauthorized changes. It also keeps a history of all the past successful connections. 

AVS Firewall is compatible with all versions of windows from Windows XP or later.


In conclusion, I would say the list of open-source firewalls is endless, in addition to the free firewalls, I would go the extra mile to add the functionality of your freeware by adding a subscription to enjoy all the features of those free firewalls. Thank me later.