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Best free Linux firewalls of 2021: go beyond iptables for desktops and servers

Best free Linux firewalls
(Image credit: Shutterstock)
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REASONS TO BUY
REASONS TO AVOID
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REASONS TO BUY
REASONS TO AVOID

In a sense, Linux has a firewall built right into the kernel itself. That said, it isn’t the most convenient to use. 

There are several graphical utilities that can help you manage it, but its protection is restricted to your Linux installation. What about the other devices in your network? 

Whether you are a home user or manage a small business, chances are you have multiple devices connected to the Internet. In addition to the computers, it’s also fairly common for establishments of all sizes to have a slew of IoT devices as well that need to be protected from the rouge elements on the Internet.

A dedicated firewall stands between the internet and sanitizes all traffic before it reaches your internal network. 

While it takes quite some skill to set one up from scratch, there are several specialized distros that will help you set up a dedicated firewall with ease.

These are the best Linux VPN providers

Best Firewall distros at a glance:

  1. IPFire
  2. OPNsense
  3. pfSense
  4. ClearOS
  5. OpenWRT

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(Image credit: IPFire)

1. IPFire

An easy-to-use firewall with some super-advanced features

Reasons to buy
+Simple to set up+Multiple deployment options+Pakfire package management

IPFire is a Linux-based stateful firewall distro that’s built on top of Netfilter. It began as a fork of the IPCop project, but has since been rewritten based on Linux From Scratch. IPFire can be deployed on a wide variety of hardware, including ARM devices such as the Raspberry Pi.

Owing to its minimalist nature, IPFire is more approachable compared to some of its peers. The installation process allows you to configure your network into different security segments, with each segment being colour-coded. The green segment is a safe area representing all normal clients connected to the local wired network. The red segment represents the internet. No traffic can pass from red to any other segment unless you have specifically configured it that way in the firewall. 

Besides its firewalling features, IPFire also has intrusion detection and prevention capabilities, and can also be used to offer VPN facilities. The distro can also be fleshed out using a handy set of add-ons to give it additional functionalities.

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(Image credit: OPNsense)

2. OPNsense

Security-minded fork of the original pfSense project

Reasons to buy
+Feature-rich+Based on HardenedBSD+Regular security updates

OPNSense is derived from the efforts of two mature open source projects, namely pfSense and m0n0wall. 

Instead of using Linux, OPNsense is powered by HardenedBSD, which is a security oriented fork of FreeBSD. The firewall distro is designed to serve as a firewall and routing platform and besides filtering traffic can also be used to display a captive portal, shape traffic, detect and prevent intrusions, as well as setup a Virtual Private Network (VPN), and lots more.

In its bid to respond to threats in a timely fashion, the firewall distro offers weekly security updates. One of the best features about OPNsense is that it exposes all its functionalities from inside a web-based interface, which is a pleasure to use and is available in multiple languages.

OPNsense implements a stateful firewall and enables users to group firewall rules by category, which according to its website, is a handy feature for more demanding network setups.

The firewall uses an Inline Intrusion Prevention System. This is a powerful form of deep packet inspection whereby instead of merely blocking an IP address or port, OPNsense can inspect individual data packets or connections and stop them before they reach the sender if necessary. 

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(Image credit: pfSense)

3. pfSense

Feature-rich FreeBSD-based firewall and router

Reasons to buy
+Clean interface+Chock full of features+Well documented

pfSense describes itself as the most trusted open source firewall. The original FreeBSD-based firewall distro, pfSense shares many similarities with OPNsense. For instance, in addition to being a powerful, flexible firewalling and routing platform, it includes a long list of related features. To begin with, just like with OPNsense, you can use pfSense to deploy an intrusion prevention system as well as enable VPN access. 

Also, like all of its peers, you can manage pfSense entirely via an intuitive web interface. Unlike most of its peers though, pfSense is available as a hardware device, virtual appliance, and downloadable community edition. 

Owing to its rich history, pfSense perhaps has the most extensive documentation, and one of the biggest communities of users that posts tutorials, and videos on its official support channels as well as elsewhere on the web. The commercial hosts of the distro also offer paid training courses to help you make best use of your pfSense deployment.

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(Image credit: ClearOS)

4. ClearOS

A well thought-out distro that's refreshingly easy-to-use

Reasons to buy
+Easy to manage+Expands to suit your needs+Ample documentation

ClearOS is a CentOS-based distro that’s designed as a full featured replacement to commercial server distros like Red Hat Enterprise Server or Windows Small Business Server. 

There are several editions of ClearOS including a community-supported edition that is offered as a no-cost free download. You can use the community edition of ClearOS to roll out all kinds of network services including a firewall, with content filtering and intrusion detection capabilities. 

The best thing about ClearOS is its ease of deployment. As most firewall distros are written for the stereotypical geek, it's nice to see a refreshing change in what seems to have become the de facto standard of 'cobble it together and think about the interface afterwards'. 

Once installed, you can administer your ClearOS-powered firewall from a web-based management interface. The administration interface is intuitive to use, and will not only help you configure and monitor your firewall, but can also be used to flesh out the distro for several other network services with a few clicks. 

To top it off, ClearOS has lots of documentation to handhold first time users through some of the most common tasks. In fact, even the interface itself has lots of useful pointers to guide you through the setup and administration process.

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(Image credit: OpenWRT)

5. OpenWRT

Veteran firewall for routers

Reasons to buy
+Best Wi-Fi support+Blazingly fast+Large cache of addons

OpenWRT is a little bit different than most on this list, as it's a firewall developed specifically for use in routers and networks. This means that it's not intended for ordinary home users looking to simply install a new firewall on their machine, as much as power users, networking enthusiasts, and wireless device developers.

OpenWRT isn't at all a new player. Not only has it been going for over 15 years but it is still very actively developed and supported, while other once popular firewall developments for distros have fallen by the wayside.

It also has a surprisingly decent GUI, and offers a number of optional packages in its repository to allow OpenWRT to be configured in a variety of ways for all kinds of uses. Despite all its flexibility, OpenWRT is still one of the least demanding distros, and is fast to run.