How to secure a Linux system

Last updated on July 9th, 2018Every Linux system will benefit from more security, especially if it contains sensitive data. With so many resources available on the internet, one might think that securing Linux has become easy. We know it is not. Linux system hardening takes a good amount of understanding about how the Linux kernel works. It also requires a good understanding of the operating system principles. In this guide, we will help you to get this understanding and provide you […]

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Ubuntu system hardening guide for desktops and servers

Last updated on July 18th, 2018The system hardening process of a system is critical during and after installation. It helps the system to perform its duties properly. This blog post shows you several tips for Ubuntu system hardening. It will dive into the most critical steps to take first. Then more specific hardening steps can be added on top of these. As most security guides only tell you what to do, we will also go into more detail on why […]

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Linux security guide: the extended version

Last updated on June 24th, 2018Feeling overwhelmed with the resources available to secure your Linux system? With this Linux security guide, we walk step-by-step through the options, tools, and resources. After reading this article, you will be able to make educated decisions about what Linux security defenses to implement for your systems. You will be introduced to the right tools that help you automate and test your improvements. Instead, related articles and resources will be available in the text. The goal is […]

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How much system hardening should you do?

Last updated on February 27th, 2017System Hardening When it comes to Linux system hardening there is a lot to do. From the almost book-like CIS benchmarks to following best practices found all over the web. Recently someone new to the field of information security asked me a simple, yet important questions: how much system hardening should you be doing? When is it enough? Since there was no easy answer, I have written down my thoughts to help others in the future. […]

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Security Defenses to Fortify your Linux Systems

Last updated on February 26th, 2016How to Fortify your Linux Systems Create a Linux security fortress; implementing security defenses using towers, bridges, and guards. Still many companies have difficulties implementing basic security measures. Even after years of websites being defaced, and customer records stolen, the same mistakes are made over and over again. While this all might sound like an unsolvable situation, information security is getting attention from more people. If you are responsible for the system management of Linux […]

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Forget Linux Vulnerability Scanning: Get Better Defenses

Building Defenses Beyond Linux Vulnerability Scanning Every month or so, I get a few questions about the vulnerability capabilities Lynis has to offer. It made me think about this subject and I realized something: Many security professionals are still focusing too much on vulnerabilities. They want to know their security gaps, so they can know where they stand. While this isn’t a bad approach, there might be a better solution. The solution I will discuss today is to focus on (permanent) […]

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Increase kernel integrity with disabled Linux kernel modules loading

Last updated on October 7th, 2015Increasing Linux kernel integrity Disable loading kernel module on Linux systems The Linux kernel can be configured to disallow loading new kernel modules. This feature is especially useful for high secure systems, or if you care about securing your system to the fullest. In this article, we will have a look at the configuration of this option. At the same time allowing legitimate kernel modules to be loaded. Disable kernel modules Newer kernel modules have a […]

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Lock Down Strategies for Linux Servers

Locking Down Linux: Strategies Most of the security defenses on Linux, are based on the earlier performed hardening activities. By locking down components on the system, the chance of a full compromise is lowered. This step-by-step locking down is a time consuming process. Time to review some of the strategies which can be applied when you want to secure your systems. Strategy 1: Locking down processes The first area to lock down are system processes. After all, each system needs […]

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Find the alternatives: CIS-CAT auditing tool

Alternatives to the CIS-CAT auditing tool The Center for Internet Security, CIS for short, is the organization behind several in-depth hardening guides. The quality of these hardening guides is outstanding, with a high level of detail. This high level of detail has one downside: it costs a lot of time to read, try and test the recommendations. Sometimes we simply don’t have the time to do an extensive audit by hand. Let alone the time to actually repeat the auditing […]

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5 Basic Principles of Linux System Security

5 Basic Principles of Linux System Security It is still common that people do not know where to start when it comes to information security. With 5 basic principles we can improve the Linux system security and question ourselves if we have done enough.   1. Know your system(s) The first principle is about knowing what your system is supposed to do. What is its primary role, what software packages does it need and who needs access? By knowing the […]

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Why Linux Security Hardening Scripts Might Backfire

Why Linux Security Hardening Scripts Might Backfire System administrators and engineers love to automate things. In the quest to get everything replaced by a script, automated hardening of systems is often requested. Unfortunately this automation might later backfire, resulting in a damaged trust in system hardening. Why System Hardening? The act of increasing system defenses is a good practice. It helps protecting your valuable data, so it can only be used by authorized people. System hardening itself consists of minimizing […]

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Using Open Source Auditing Tools as alternative to CIS Benchmarks

Last updated on June 22nd, 2018Using Open Source Auditing Tools An alternative to CIS Benchmarks and hardening guides Hardening guides, and the CIS benchmarks in particular, are a great resource to check your system for possible weaknesses and conduct system hardening. But who has the time to read it cover to cover, and apply every single step? In this article, we have a look at the alternative: open source auditing tools. Time.. Hardening is a time-consuming task. As security specialists, […]

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Disable SSLv3 in Lighttpd to protect against POODLE attack

Disable SSLv3 in Lighttpd Protecting against the POODLE attack The POODLE attack has entered the news a few times now. The issue behind the POODLE attack is serious, as it abuses a weakness in the protocol, not the implementation. This means the only proper fix is abandoning the SSLv3 protocol and use the newer TLS protocols. Disable SSLv2 and SSLv3 Lighttpd commonly has its configuration settings stored in /etc/lighttpd/lighttpd.conf. Open this file and add the following two statements, to disable […]

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Finding setuid binaries on Linux and BSD

Finding setuid binaries for Linux and BSD systems Why setuid? Binaries with the setuid bit enabled, are being executed as if they were running under the context of the root user. This enables normal (non-privileged) users to use special privileges, like opening sockets. While this seems unnecessary for a normal user, it is actually needed for simple commands like ping. Finding files with setuid bit To discover all files with the setuid bit, we can use the find command. Depending […]

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Linux capabilities 101

Last updated on July 15th, 2018Even seasoned Linux administrators may not be very aware of Linux capabilities. Still, they are used a lot and apply to most systems. This feature was added to Linux 2.2 kernel and gave us new possibilities regarding security. In this guide, we have an in-depth look how can leverage them.   What are Linux capabilities? Linux capabilities divide the privileges of the superuser into smaller and distinctive units. These units can then be independently be applied to […]

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