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

Linux Security Guide for Hardening IPv6

Linux Security Guide for Hardening IPv6 Version 6 of Internet Protocol is now 20+ years available. You would think it is widely available now, right? Not exactly. Still many internet providers don’t have it deployed for their customers. Hosting companies are not always eager to deploy it either. Mostly because of lacking knowledge. To get at east more knowledge shared on the security side of IPv6, we have crafted this guide. Hopefully it will be a practical guide for your […]

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How to Determine a File Type on Linux

Finding Files and Understanding Their Content You may encounter a file on your system with known contents or goal. Usually, the first thing we do is then use cat to show the contents, or execute it. While that makes sense, it may be dangerous to do. It might be a piece of malware, disrupt your screen output or even hang the terminal. Here is a better way to do it, using the file command. Great for forensics, malware analysis, intrusion […]

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Hardening WordPress Security and Reduce Information Disclosure

WordPress and Reducing Information Leakage For years, WordPress is used as a platform for blogging. Last years, more and more companies have even built their website in WordPress. Unfortunately, this also means it is more often targetted by scripts, searching for their next victim. The primary reasons for a WordPress hack, are often disclosed information and outdated software components. This is applicable to the WordPress version itself and modules, like the plugins. In this article, we have a look at dealing […]

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Granting Temporary Access to Your Servers (Using Signed SSH Keys)

Temporary access with SSH In need of support from a colleague or vendor, but don’t want to give them permanent access? SSH has an option to allow temporary access! Next time you need to provide temporary access for an hour or day, use this great option. Our Setup We have two machines for this purpose. One is a system running Arch Linux, the client system. The other one is a server, running Ubuntu Linux. For temporary support, we have created a […]

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Distributing SSH keys: using ssh-copy-id, manually or automated

Distribution of SSH keys When you want to allow public key authentication, you have to first create a SSH keypair. Next step is then the distribution of the public key to the other systems. Let’s have a look at a few options, including using the ssh-copy-id utility. Option 1: Manually In the past, you had to log in manually to the new system and do things yourself. Especially if you created your key with a tool like PuTTYgen on Windows. […]

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Create random passwords with OpenSSL/LibreSSL

Random Passwords Generation As system administrators, we know we sometimes have to create passwords. It might be for ourselves, or when creating them for colleagues and customers. For an easy and quick way of generating random passwords, we can use the OpenSSL utility, part of OpenSSL and LibreSSL. This toolkit is often already installed on systems running Linux. OpenSSL has a randomize function. If we feed the output through the base64 function, the scrambled set of characters can be made more […]

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Block IP addresses in Linux with iptables

Blocking IP addresses and subnets with ipset Most system administrators will already be familiar with iptables. It is around for quite a while and is enabled by default within the Linux kernel. We can use iptables to block one, multiple IP addresses, or even full networks. This may come in handy when you get repeating port scans or see failed login attempts in your log files. Time to get started and block some IP addresses! Check existing iptables configuration The first step is to […]

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How to Disable “System program problem detected”

Quick Ubuntu Tips: System program problem detected   Sometimes programs crash, usually for a different variety of reasons. While it is good to do research and find the underlying cause, sometimes you simply want to disable any reporting. Clean up /var/crash First thing to do is check your /var/crash directory and see if there are any “crash” files. These are just normal text files and include details about a process. If you have a process crashing regularly, you most likely want to […]

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