In the world of cybersecurity, firewalls are often heralded as the gatekeepers of network security. Yet, beneath their glossy marketing sheen lies a sobering truth: the very foundation of most commercial firewalls, their kernel, is a cobbled-together relic forked from the Linux kernel many years ago. This outdated and Frankenstein-like architecture poses a significant and ongoing risk to the businesses that rely on it.
The False Premise | "Our Developers Are Better Than Linux’s"
Firewall vendors often operate under the misguided assumption that their proprietary kernel, a heavily modified fork of the Linux kernel, is superior to the original. This belief rests on the idea that commercial developers somehow possess more skill or insight than the global team of contributors driving the Linux project. This premise is not just arrogant; it’s patently false.
Linux: The Innovator and Custodian
The Linux kernel is maintained and advanced by an open-source community that includes some of the brightest minds in computing, backed by decades of collaborative innovation. This community operates under the principle of transparency, ensuring that the kernel undergoes rigorous scrutiny by developers worldwide.
Firewall Vendors: Patchwork Peddlers
In contrast, firewall vendors fork the Linux kernel, make modifications to suit their proprietary systems, and lock the code behind closed doors. Over time, these kernels diverge so significantly from the original Linux project that they become patchwork monstrosities, poorly equipped to integrate the latest security updates or performance enhancements.
A Kernel Stuck in the Past
Most commercial firewall kernels are based on Linux kernels that are now four or more major releases behind the current version. In the fast-moving world of cybersecurity, this is akin to using a stone axe in a digital arms race. Here’s why this lag is so dangerous:
Vulnerability Accumulation
With each new Linux kernel release, countless vulnerabilities are patched, and security mechanisms are improved. Forked firewall kernels, however, often lack these critical updates because retrofitting modern patches onto a decades-old foundation is practically impossible.
Stunted Innovation
By isolating themselves from the Linux community, firewall vendors miss out on innovations like improved memory safety, advanced networking capabilities, and more robust security features.
Opaque Code
The closed-source nature of these kernels means they cannot be audited by independent researchers. Unlike Linux, which benefits from the "many eyes" principle, these firewalls operate in the shadows, leaving vulnerabilities to fester until they are inevitably exploited.
The Real-World Impact
The consequences of relying on outdated kernels are evident in the litany of vulnerabilities reported in commercial firewalls year after year. These are not theoretical risks—they are practical realities:
High-Profile Compromises
Businesses and institutions that depend on firewalls with vulnerable kernels are routinely breached. The root cause often traces back to the kernel's inability to withstand modern attack vectors.
Patchwork Patching
Vendors attempt to retroactively apply patches to their legacy kernels, but these fixes are often superficial, addressing symptoms rather than underlying architectural flaws.
False Sense of Security
Many cybersecurity professionals exhibit a blind faith in firewalls, trusting them as infallible guardians of their networks. This misplaced loyalty leads businesses to overlook more fundamental, cost-effective, and secure alternatives.
The Risk of Closed Source
The closed-source model of most commercial firewalls is a significant liability. Unlike open-source Linux, where vulnerabilities are openly identified and resolved, proprietary kernels rely on the secrecy of their code. This secrecy doesn’t make them secure—it simply delays the inevitable discovery and exploitation of their flaws.
Linus Torvalds vs. Firewall Vendors
Let’s be blunt: no developer employed by a firewall vendor can credibly claim to be a better kernel developer than Linus Torvalds and the Linux community. Torvalds and his collaborators have built a kernel that powers everything from supercomputers to smartphones, with a relentless focus on stability, performance, and security. The notion that a team of commercial developers working in isolation could surpass this collective effort is laughable.
What’s the Alternative?
The overreliance on traditional firewalls needs to be reevaluated. Instead of investing in overpriced, outdated, and inherently flawed magic boxes, businesses should focus on pragmatic, effective security strategies:
Embrace Modern Network Design
Adopt a zero-trust architecture and focus on segmentation, host-level firewalls, and secure configuration management. These approaches reduce reliance on perimeter-based defences.
Use Open-Source Firewalls
Platforms like pfSense and OPNsense, built on modern, open-source kernels, offer transparency and flexibility. They allow businesses to benefit from the latest security advancements without vendor lock-in.
Invest in People and Processes
Security is not a product—it’s a practice. Training employees, implementing robust policies, and conducting regular audits are far more effective than relying on any single piece of hardware.
Focus on Risk Mitigation
Security tools should align with your business risk profile. Avoid feature bloat and focus on solutions that provide real value rather than ticking marketing checkboxes.
Wrap | The Firewall Snake Oil
Firewalls built on outdated and proprietary kernels are a classic case of cybersecurity snake oil. They promise much but deliver little beyond a false sense of security and an inflated budget line item. It’s time for businesses to question the blind loyalty they place in these products and prioritise strategies and technologies that genuinely enhance their security posture.
The Linux kernel is a shining example of what transparency, collaboration, and innovation can achieve. It’s a shame that firewall vendors chose to fork away from this success story, leaving their customers to bear the consequences of their hubris.
