Before going through the list of the best free and open-source Linux firewall software, you may want to know in detail what is a Linux Firewall, how it works, and what it does for you in our detailed Linux Firewall article.
Open-Source Firewalls for Your Linux System
Since this article focuses on firewalls’ software aspects, we can never run out of lack in our Linux firewall quests. However, we only need to deal with firewall popularity and effectiveness. Therefore, the list of firewalls that best suite our requirements are as follows:
Iptables is a common name in the firewall domain. It is also called Netfilter. Its popularity with Linux systems is from its terminal-based implementation. A Linux server admin that wants to gain some confidence with firewall configurations should start with this software to fine-tune their network servers’ performance. A network’s data packet filtering tasks take place from the system kernel. The features and attributes of this firewall are as follows:
- It has packet filter rulesets that support content listing.
- Implements a packet header inspection approach, which makes the firewall conveniently fast.
- Editable packet filter rulesets enable a user to add, edit, or remove a firewall configuration rule.
- You can use it for datafile backup and restoration tied to the firewall’s functionality.
2. IPCop Firewall
The Linux firewall distribution responsible for this open-source firewall made is user-friendly, stable, highly configurable, and secure. It is pre-packaged with a modern web interface to make it easy to manage. Local PCs and small businesses will never run out of reasons not to use this firewall. A practically viable approach to implementing this firewall is to set it up on an old PC that functions as a secure VPN. Therefore, this new environmental setup will manage and determine the authenticity and authorization of any other connection transmitted from the internet. Its users enjoy an improved web browsing experience that the firewall provides because it caches frequently used information. We can summarize its features in the following bullet points.
- The web interface it provides is color-coded. Therefore, you can easily monitor the network’s throughput, the network machine’s disk, memory, and CPU performance through displayed graphical icons.
- Supports multiple user languages
- It is easy and secure to add on patches and implement feature upgrades.
The popularity of this open-source firewall binds it to a GNU/Linux environment. The Linux kernel is known for its integration with a Netfilter system. It is from this system that a basis is provided for the development or creation of this firewall. Its features can be summarized as follows:
- Supports VPN
- Supports port forwarding and masquerading
- Supports multiple ISP
- A Webmin Control Panel is part of its GUI interface
- Centralized firewall administration
- Supports numerous gateway, routers, and firewall applications.
- It manages stateful packet filtering through Connection Tracking Facilities provided by Netfilter.
4. UFW – Uncomplicated Firewall
All Ubuntu servers are defaulted by this firewall. Its design objective was to come up with a firewall less complex than Iptables and, at the same time, user-friendly. The firewall also packages a GUI called GUFW, which is at Ubuntu and Debian users’ disposal. We can summarize its features as follows:
- Supports IPV6
- Status monitoring
- It’s extensible; hence other applications can integrate it
- You can add, remove, or modify firewall rules to your preference
- Has an On/Off facility as an extension of its logging options
The power of this Linux firewall manager is in its simplification of the Iptable rules for a target network or server. You do not need to be a student of the Iptables to master this firewall. It is user-friendly and will take you little time to master its administration. Its features are as follows:
- Traffic shaping
- Easily configurable through NAT
- IPV6 support
- Real-time bandwidth usage and connection monitoring
FreeBSD servers praise the reliability of this open-source firewall. It conceptualizes Stateful Packet filtering, and the features packaged with it are also available in premium or commercial firewalls with a heavy price tag. Its prime features are as follows:
- Load balancing for inbound and outbound traffic
- Provides the server’s real-time information and caters for traffic shaping
- Its configuration can make it function as a VPN endpoint and as a wireless access point
- It is deployable as a DHCP & DNS server, a firewall, and as a router
- Has a web-based interface from which it can be upgraded or flexibly configured
This open-source firewall works best in a Small Office Home Office (SOHO) setting or environment. It is highly flexible and with a lot of modular considerations in its design. It also qualifies as an SPI (Stateful Packet Inspection) firewall due to its community’s security and development efforts. A summary of its features are as follows:
- Content filtering
- Multi-deployment facilitation can be as a VPN gateway, a proxy server, or as a firewall.
- Its support extends to Chats, Forums, and Wiki.
- Provides a virtualization environment through its support for hypervisors like Xen, VMWare, and KVM
- Has an inbuilt functionality for detecting system intrusions
8. SmoothWall and SmoothWall Express
The web-based interface provided by this open-source firewall is highly configurable. This interface is referred to as a Web Access Manager or WAM. SmoothWall Express is SmoothWall’s freely distributable version. Its features are as follows:
- Proxy support
- HTTPS filtering
- Real-time content filtering
- Enables the monitoring of firewall activities and log views
- Supports wireless networks, DMZ, and LAN
- Implements traffic stats management based on the site’s visits and used IP
This open-source firewall also conceptualizes Stateful Packet Inspection. Its deployment can be a Gateway VPN, proxy, or routers. The IPCop firewall provided the foundation for its development. Its prime features are as follows:
- VPN support with IPSec
- Snort intrusion prevention
- Bidirectional firewall
- Network traffic logging in real-time
- Provides mail servers security through Spam Auto-Learning, SMTP proxies, Greylisting, and POP3 proxies.
- Provides web server security through URL blacklist, antivirus, HTTP & FTP proxies.
10. ConfigServer Security & Firewall (CSF)
This open-source firewall’s versatility makes it a cross-platform software. It also conceptualizes SPI (Stateful Packet Inspection). The firewall can host or facilitate numerous virtual environments like VMware, Virtuozzo, XEN, OpenVZ, Virtualbox, and KVM. Its known features include:
- Checks for network exploits
- Its intrusion detection system mechanism is advanced
- Can shield a Linux box from the ping of death and syn flood attacks
- Easy to manage and configure
- Can work with a configured email alert system to send notifications on unusual network activities or detected intrusions.
A firewall keeps your network healthy by increasing the performance of both the server and the network computer and machines. It keeps a network secure and organized because of the authentication and authorization protocols it puts in place. The firewall you want to put in place should consider the network infrastructure’s size, security layers required, and the number of network devices you want to manage.