2014-11-27 Michael BoelenDevelopment, Hardening, Software Leave a comment

Protect against ptrace of processes: kernel.yama.ptrace_scope

Protect against the usage of Ptrace Hardening the kernel with kernel.yama.ptrace_scope Ptrace is a great troubleshooting tool for developers to determine how a process functions. It can be used to find programming flaws, like memory leakage. On the other hand, the tool also be used by people with malicious intent. For example to debug a process as a non-privileged user and find the contents of application memory. Yama Linux has the ability to include Linux Security Modules, to provide additional […]

2014-11-21 Michael BoelenHardening, Network 14 comments

Filtering ARP traffic with Linux arptables

Filtering ARP traffic with Linux arptables Most Linux system administrators will be familiar with iptables on Linux. Less known is the arptables utility, which controls filtering arp packets. Installation The arptables utility is easy to set-up, as the main functionality is already implemented in the Linux kernel. Just install the arptables package on your favorite Linux distribution. Red Hat / CentOS / Fedora yum install arptables Debian / Ubuntu apt-get install arptables Configuration example To show the effect of filtering […]

2014-11-15 Michael BoelenHardening, System Administration 16 comments

Linux Capabilities: Hardening Linux binaries by removing setuid

Linux Capabilities Hardening Linux binaries by removing setuid Normally Unix based systems use two kind of processes: privileged and unprivileged. The first category is usually used for administrative purposes, like starting and stopping other processes, tuning the kernel and opening sockets. Root permissions The command ping is a great example why even small programs needs root permissions. In a first glance you might consider this tool to be simple: send a package to a host and see if it responds. The […]

2014-11-06 Michael BoelenHardening, Storage Leave a comment

Securing mount points on Linux

Securing mount points Mount points are defined in /etc/fstab. They link a particular disk pointer to the related device (disk, partition or virtual device). By default the mount options are not focused on security, which gives us a room to further improve hardening of the system. This hardening is especially important considering our most precious data is stored here. Via mount options we can apply additional security controls to protect our data. Mount points Let’s have a look at our […]

2014-11-01 Michael BoelenAuditing, Automation, Configuration Management, Hardening, Lynis, Monitoring, Software, System Administration Leave a comment

Alternatives to Bastille Linux: system hardening with Lynis

System hardening with Lynis Many people used Bastille Linux to harden their Linux systems. Unfortunately the website of Bastille seems very outdated, including the tool. This resulted in people searching for a great alternative to replace this tool. We found the alternative by actually combining different solutions, being more powerful. Security automation is hot, so forget Bastille and do it the right way. Automatic hardening makes sense Most system administrators can’t keep up with the new technologies and security threats. […]

2014-08-27 (last updated at April 5th, 2017) Michael BoelenHardening, Software 3 comments

Protect against the BEAST attack in Nginx

Protect against the BEAST attack in Nginx What is this BEAST? BEAST, or “Browser Exploit Against SSL/TLS” is an attack against the cipher block chaining (CBC) method used with SSL/TLS. The weakness was discovered in 2002, but finally proven in 2011 by security researchers Thai Duong and Juliano Rizzo. With real proof of concept code, they showed it was no longer a theoretical attack. To successfully perform the BEAST attack, there are some conditions which needs to be met: Vulnerable version of […]

2014-08-12 (last updated at February 12th, 2019) Michael BoelenHardening, Software, Web 2 comments

Configure HSTS (HTTP Strict Transport Security) for Apache and Nginx

HSTS configuration for Apache and Nginx HTTP Strict Transport Security (or HSTS) is a security capability to force web clients using HTTPS. The idea behind HSTS is that clients which always should communicate as safely as possible. At achieve this, the web server and web browser will prefer the HTTPS protocol instead of HTTP. Benefits The clear benefit of “forcing” a client to use HTTPS directly, is decreasing the risk of sharing any sensitive information via a protocol which can […]

2014-07-24 (last updated at October 20th, 2014) Michael BoelenAuditing, Compliance, Hardening Leave a comment

Do NOT use Linux hardening checklists for your servers

Do NOT use Linux hardening checklists for your servers Quality is an interesting word. It describes, well, the quality of something. Quality is just another word for how well can you repeat something. The goal is to get each time exactly the same result. Whenever it’s a physical product, or rolling out a new Linux system, you want great quality. One method to increase quality is using checklists. However we strongly advice against using Linux hardening checklists.. But checklists are […]

2014-06-12 (last updated at January 30th, 2015) Michael BoelenAuditing, Hardening, Linux

Hardening Guides and Tools for Red Hat Linux (RHEL)

Hardening Guides and Tools for Red Hat Linux (RHEL) System hardening is an important part in securing computer networks. Each system should get the appropriate security measures to provide a minimum level of trust. In this post we have a look at some of the options when securing a Red Hat based system. This information applies to Red Hat Linux (RHEL), Fedora, CentOS, Scientific Linux and others. Red Hat Red Hat itself has a hardening guide for RHEL 4 and […]

2014-05-30 (last updated at July 7th, 2018) Michael BoelenHardening Leave a comment

Linux hardening steps for starters

Most systems have confidential data that needs to be protected. To safeguard this data, we need to secure our Linux system. But how to properly harden a Linux system? In this article, we will cover this step by step. We start by with physical security measures to prevent unauthorized people from access the system in the first place. Next is doing the installation the right way, so we have a solid foundation. Finally, we will apply a set of common […]

2014-05-03 (last updated at October 20th, 2014) Michael BoelenAuditing, Compliance, Hardening, Lynis

Linux server security: Three steps to secure each system

Linux server security: Three steps to secure each system Determining the level of Linux server security can only by measuring the actual implemented security safeguards. This process is called auditing and focuses on comparing common security measures with the ones implemented. While there is almost no system with all possible safeguards implemented, we still can determine how well (or badly) the system is protected. Security is about finding the weakest link(s) and associate risk with each weakness. Depending on the […]

2014-04-27 (last updated at June 26th, 2018) Michael BoelenHardening, Kernel, Linux

Linux kernel security and how to improve it

Every system is as strong as its weakest link. In the case of an operating system like Linux, one weakness in the kernel could result in a security breach. This article covers the Linux kernel features and how they work. Kernel features Live kernel patching As the kernel is similar to other software, it receives updates to improve it. Now and then a security weakness is discovered in one of the subsystems of the Linux kernel. This means that Linux […]

2014-04-09 (last updated at October 20th, 2014) Michael BoelenAuditing, FreeBSD, Hardening, Lynis

FreeBSD hardening with Lynis

FreeBSD hardening with Lynis Lynis development has its roots on a FreeBSD system, therefore FreeBSD hardening is also easy and supported when using Lynis. People who want to audit and harden their FreeBSD system will discover Lynis to be a powerful tool for this purpose. In this article we will focus on how to audit your system with Lynis. Lynis Lynis is an open source audit tool. It only requires root access and a normal shell and the tool is […]

2014-03-27 (last updated at October 20th, 2014) Michael BoelenAuditing, Hardening, Lynis

How to use Lynis

How to use Lynis This article explains in a few quick steps how to start with using Lynis. A more extensive explanation can be found in the documentation of Lynis. Download Lynis: wget http://cisofy.com/files/lynis-version.tar.gz Unpack tarball: tar xfvz lynis-version.tar.gz This will unpack the tarball with a Lynis directory. Go into this directory: cd lynis-version When running Lynis for the very first time, just just the -c parameter. It will start the audit process and pauses after every batch of tests. […]

2014-03-12 (last updated at July 10th, 2018) Michael BoelenHardening, Lynis

Lynis Hardening Index

At the end of each Lynis scan, the report will be displayed. This report will include the findings (warnings and suggestions) and general information like the number of security tests performed. Additionally, the location of the log file and report data will be displayed. Between all this information there is a “Lynis hardening index” displayed. This index is unique to Lynis. The index gives the auditor an impression on how well a system is hardened. This number, however, is just […]

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