As cyberattacks become increasingly sophisticated, building a truly unhackable operating system may seem like an impossible task. However, by leveraging the inherent security benefits of Linux, system administrators can create an OS that comes close to being impenetrable. 

The Linux kernel itself provides a strong security foundation. Its modular architecture allows only the minimum necessary drivers and services to be loaded, reducing the attack surface area. Linux also utilizes security modules like SELinux and AppArmor for access control and mandatory access controls. These features allow fine-grained policies to be defined, restricting what resources programs and users can access.

But the OS itself is only one layer. A comprehensive security strategy needs to encompass the whole technology stack. Securing Linux requires hardening at the kernel, software, and administration levels.

Kernel Hardening

The Linux kernel can be hardened to prevent certain types of exploits. Features like address space layout randomization (ASLR) and non-executable memory segments make it difficult for attackers to inject malicious code. 

ASLR randomizes the location where executables are loaded into memory. This prevents attackers from reliably jumping to exploit code. Non-executable stacks and heaps set memory segments to non-executable, stopping shellcode from running even if injected.

Kernel hardening also includes deactivating unnecessary drivers and protocols. Attack surface can further be reduced by using a modular kernel, only loading the minimum drivers required for the system to run. 

Security modules like SELinux enforce access controls, while capabilities and namespaces compartmentalize what resources processes can access. Capabilities split root privileges amongst units, namespaces provide isolation between processes. This increases security in the event an attacker gains elevated access.

Hardening Software

But locking down the kernel is half the battle. The other crucial element is hardening userspace software. Libraries and applications running on top of the kernel increase the attack surface dramatically.

All software should run using the principle of least privilege. Containers and virtual machines can isolate services and use different resources. This ensures that if one application gets compromised, the entire system does not fall.  

Staying up-to-date with the latest security patches is critical. New vulnerabilities are constantly being discovered, so software must be maintained diligently. Automated patching systems and centralized package managers make patch management easier.

Software should also be configured securely out of the box. Developers can ship programs following security best practices for privileges, permissions, and auth controls. Disabling unnecessary features reduces risks.

Web servers and applications are common targets, so hardening measures like HTTPS everywhere, input sanitization, WAF rules, etc need deployment. SELinux and AppArmor profiles can enforce strict policies for what web apps can interact with.

Admin Hardening 

The final piece is hardening administration. Even with an unhackable kernel and software, systems are vulnerable due to misconfigurations or insider threats.

Access should be given only on a need-to-know basis following the principle of least privilege. SSH key-based authentication enhances login security over passwords. Sudo rules tightly control which users can run privileged commands.

Logging and monitoring provide visibility into all system activities. Centralized logging ensures audit records can’t be tampered with. Integrity checking detects unauthorized configuration changes.

System hardening tools like Bastille harden Linux by changing insecure default settings to adhere to CIS Benchmarks consensus security configuration standards.

Finally, the system must manage updates rapidly by having a vulnerability management system in place to scan for insecure software, missing patches, system misconfigurations and remediate them quickly by applying patches, making configuration changes automatically.

A truly secure system requires a layered defense spanning the entire technology stack. Hardening the kernel, software, and access prevents both external attackers and insider threats. Following least privilege principles, staying current, and monitoring for anomalies are key for security.

While no system can ever be 100% unhackable, leveraging Linux security capabilities makes it extremely difficult for hackers to penetrate. Even if one layer gets breached, additional inner barriers prevent a full compromise. Hardening Linux minimizes attack surfaces throughout the OS.

Of course, securing Linux is not a set-it-and-forget-it process. Threats evolve rapidly, so Linux systems need to be continually updated, monitored, and hardened against new vulnerabilities. Dedicated security teams and operations best practices are needed to truly leverage Linux’s capabilities for maximum security on an ongoing basis.