Passionate about Linux hardening, compliance, security management and new technologies.

Discover to which package a file belongs to

Related Packages and Files Sometimes you want to know the related package of a file, before installation, or when it is already there. This is of great help during system hardening or general system cleanups. In this article we have a look at several ways to determine the relationships between files and the package they belong to. We have gathered this information for multiple Linux distributions. CentOS, Fedora, RHEL Show files for RPM packages rpm -qlp /path/to/file.rpm Show files for packages on […]

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Examples on how to use the grep command

Using grep The grep command is one of the oldest tools for Linux and other platforms. Actually, it is older than Linux itself. It was written by Ken Thompson more than 45 years ago! The name grep stands for “globally regular expression print”. This name comes from its predecessor ed and the specific mode in which you would globally search, using a regular expression, and print the output. The related command was “g/re/p”. For more history, have a look at the […]

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When should you do a penetration test?

Penetration Testing and Linux The information security field is filled with all kind of tests and assessments. One of them is the penetration test, also abbreviated to pentest or pen test. Last years, many security consultancy firms offer this test as part of their security services. So what is it really and when should you undergo a penetration test? Continue reading! What is a pentest? The short question to what a penetration is: a hack attack on your environment, executed by […]

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Linux system hardening: adding hidepid to /proc mount point

Hiding processes for other users When looking in /proc you will discover a lot of files and directories. Many of them are just numbers, which represent the information about a particular process ID (PID). By default, Linux systems are deployed to allow all local users to see this all information. This includes process information from other users. This could include sensitive details that you may not want to share with other users. By applying some file system configuration tweaks, we can change […]

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How to solve an expired key (KEYEXPIRED) with apt

Updating expired keys on Debian and Ubuntu Software updates and package management is easy with systems based on Debian or Ubuntu. Just apt-get update (or apt update) and run an upgrade. But sometimes you may encounter the following situation: a KEYEXPIRED message. root# apt-get update && apt-get upgrade Get:1 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB] Hit:2 http://nl.archive.ubuntu.com/ubuntu xenial InRelease Get:3 http://nl.archive.ubuntu.com/ubuntu xenial-updates InRelease [95.7 kB] Hit:4 http://nl.archive.ubuntu.com/ubuntu xenial-backports InRelease Hit:5 https://packages.cisofy.com/community/lynis/deb stable InRelease Get:6 http://nl.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [373 kB] Ign:7 […]

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How much system hardening should you do?

System 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. Time and Effort To understand […]

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Difference between CentOS, Fedora, and RHEL

Difference between CentOS, Fedora, and RHEL The biggest open source company is nowadays Red Hat. It is known for its contributions to many open source projects, including the Linux kernel itself. Less known is that Red Hat is involved in different Linux distributions, directly or indirectly. Fedora Fedora has received many updates and individual releases over the years. It is a playground for new functionality. Often new technology is found here. It can be compared with other distributions like Arch […]

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Linux and rise of Ransomware

Ransomware on the Linux Platform Times are changing when it comes to Linux malware. Since a long time we had backdoors, PHP shells, and even rootkits. But it won’t take long that ransomware will catch up on the Linux platform. We hope you are reading this to counter the threat, not because it is already too late. Ransomware invasion Ransomware is a little devil. It encrypts your valuable data and protects it with a generated key. This key is then […]

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