Security is paramount. Security involves defense in depth. Approaching security one step at a time, with consistency and rigour, you can mitigate threats, and keep intruders at bay.

Intruders use a variety of different techniques in an attempt to compromise a system. For example, systems can be attacked by denial of service, cracking, intrusion, snooping (intercepting the data of another user), or viruses/worms/Trojan horses. To have a secure box, a system therefore needs a variety of defenses.

One important step to protect a system is using a firewall. Essentially, this is a network security system, acting like a security guard between internal and external networks. The firewall controls incoming and outgoing network traffic using security rules. The rules specify which connections you want to allow and the ports and zones through which the connection can be established.

All of the software featured in this article is released under an open source license. Each of the solutions offer a comparable set of features to many expensive commercial firewall solutions.

There are dozens of open source firewalls to download. To provide an insight into the quality of software that is available, we have hunted high and low for the finest firewall solutions. All 6 open source firewall solutions below are worthy of recommendation, but if we had to recommend a single solution, our award would go to pfSense – this is based on FreeBSD not Linux.

Firewalls pfSense Powerful firewall and routing platform based on FreeBSD ClearOS Dedicated firewall and Internet server/gateway Untangle Quality open source alternative to SonicWALL and WatchGuard IPFire Distro with a versatile and state of the art firewall engine Smoothwall Express Firewall with its own security-hardened Linux distro Shorewall High-level tool for configuring Netfilter

Return to our complete collection of recommended free and open source software including our latest additions.

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