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How Secure Is Linux?

How Secure Is Linux?

It is no secret that the OS you choose is a key determinant of your security online. After all, your OS is the most critical software running on your computer - it manages its memory and processes, as well as all of its software and hardware. The general consensus among experts is that Linux is a highly secure OS - arguably the most secure OS by design. This article will examine the key factors that contribute to the robust security of Linux, and evaluate the level of protection  against vulnerabilities and attacks that Linux offers administrators and users.

Secure by Design

When it comes to security, Linux users are at a decided advantage over their Windows- or Mac- using counterparts. Unlike proprietary OSes, Linux in many ways has security built into its core design. The increasingly popular open-source OS is high flexibility, configurable and diverse. It also implements a strict user privilege model and offers a selection of built-in kernel security defenses to safeguard against vulnerabilities and attacks. The transparency of Linux source code means that vulnerabilities in it - which are inevitable to some degree in any OS - are almost always short-lived. Let’s take a closer look at each of these factors and how it contributes to the heralded security of Linux.

The Open-Source Security Advantage

Linux source code undergoes constant, thorough review by members of the vibrant, global open-source community and, as a result of this scrutiny, Linux security vulnerabilities are generally identified and eliminated very rapidly. In contrast, proprietary vendors like Microsoft and Apple employ a method known as “security by obscurity”, where source code is hidden from outsiders in an attempt to conceal vulnerabilities from threat actors. However, this approach is generally ineffective in preventing modern exploits and, in reality, undermines the security of the “hidden” source code by preventing outsiders from identifying and reporting flaws before they are discovered by malicious actors. Let’s face it - when it comes to discovering security bugs, a small team of proprietary developers is no match for the worldwide community of Linux user-developers who are deeply invested in their work both for their own benefit and for the benefit of the community.

A Superior User Privilege Model

Unlike Windows where “everyone is an admin”, Linux greatly restricts root access through a strict user privilege model. On Linux, the superuser owns all the privileges, and ordinary users are only granted enough permissions to accomplish common tasks. Because Linux users have low automatic access rights and require additional permissions to open attachments, access files, or adjust kernel options, it is harder to spread malware and rootkits on a Linux system. Thus, these inherent restrictions serve as a key defense against attacks and system compromise.

Built-In Kernel Security Defenses

The Linux kernel boasts an array of built-in security defenses including firewalls that use packet filters in the kernel, the UEFI Secure Boot firmware verification mechanism, the Linux Kernel Lockdown configuration option and the SELinux or AppArmor Mandatory Access Control (MAC) security enhancement systems. By enabling these features and configuring them to provide the highest level of security in a practice known as Linux kernel self-protection, administrators can add an additional layer of security to their systems. 

Security through Diversity 

There is a high level of diversity possible within Linux environments as a result of the many Linux distributions (distros) available and the different system architectures and components they feature. This diversity not only helps satisfy users’ individual requirements, it also helps protect against attacks by making it difficult for malicious actors to efficiently craft exploits that can be used against a wide range of Linux systems. In contrast, the homogeneous Windows “monoculture” makes Windows a relatively easy and efficient attack target.

In addition to the design diversity seen in Linux, certain secure Linux distros are differentiated in ways that specifically address advanced security and privacy concerns shared among pentesters, reverse engineers and security researchers.

Highly Flexible & Configurable 

There are vastly more configuration and control options available to Linux administrators than to Windows users, many of which can be used to enhance security. For instance, Linux sysadmins have the ability to use SELinux or AppArmor to lock down their system with security policies offering granular access controls, providing a critical additional layer of security throughout a system. Admins can also use the Linux Kernel Lockdown configuration option to strengthen the divide between userland processes and kernel code, and can harden the sysctl.conf file - the main kernel parameter configuration point for a Linux system - to give their system a more secure foundation.

Linux: An Increasingly Popular Target among Cyber Criminals

Linux powers the majority of the world’s high-value devices and supercomputers and the OS’s user base is steadily growing- and cyber criminals have taken note of these trends. Malware authors and operators are increasingly targeting Linux systems in their malicious campaigns. The past few years have been plagued with emerging Linux malware strains - Cloud Snooper, EvilGnome, HiddenWasp, QNAPCrypt, GonnaCry, FBOT and Tycoon being among the most notorious. That being said, Linux is still a relatively small target, with 83% of malware targeting Windows systems in 2020. Furthermore, the recent increase in Linux malware attacks is not a reflection on the security of Linux. The majority of attacks on Linux systems can be attributed to misconfigurations and poor administration, highlighting a widespread failure among Linux sysadmins to prioritize security.

Luckily, as Linux malware continues to become increasingly prevalent and problematic, Linux features built-in protection against malware attacks through its strict user privilege model and design diversity, and there is a selection of excellent reverse engineering and malware scanning tools, toolkits and utilities including REMnux, Chkrootkit, Rkhunter, Lynis, and Linux Malware Detect (LMD) available to help admins detect and analyze malware on their systems.

The Bottom Line

The security of the OS you deploy is a key determinant of your security online, but is by no means a sure safeguard against malware, rootkits and other attacks. Effective security is dependent upon defense in depth, and other factors including the implementation of security best practices and smart online behavior play a central role in your digital security posture. That being said, choosing a secure OS is of utmost importance, as the OS is the most critical piece of software running on your computer, and Linux is an excellent choice as it has the potential to be highly secure - arguably more so than its proprietary counterparts - due to its open-source code, strict user privilege model, diversity and relatively small user base.

However, Linux is not a “silver bullet” when it comes to digital security - the OS must be properly and securely configured and sysadmins must practice secure, responsible administration in order to prevent attacks. Also, it is crucial to keep in mind that security is all about tradeoffs - both between security and usability and between security and user-friendliness. LinuxSecurity Founder Dave Wreski explains, “The most secure system is one that is turned off, covered in cement, and located at the bottom of the ocean - but this system is obviously not very usable. Admins should configure their systems to be as secure as is practical within their environment. In regards to convenience, Linux has a bit of a learning curve, but offers significant security advantages over Windows or MacOS. It’s a tradeoff that’s well worth it if you ask me.”

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