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 […]

Read more

The Difference Between Auditing and Vulnerability Scanning

Technical Auditing and Vulnerability Scanning Why both look the same, yet have subtle differences When talking about auditing, I see that most technical people immediately think about vulnerability scanning. While they definitely have things in common, there are also a lot of minor differences. In this blog post I will show them, and also share how technical auditing and vulnerability scanning can work together. Similarities and Differences Let’s first determine what makes technical auditing and vulnerability scanning look similar. First […]

Read more

Tiger is History, Long Live Modern Alternatives!

The History and Alternatives to the Tiger Security Tool Recently I saw some tweets showing up from an old friend: Tiger. Surprised to see it being promoted, as I know the tool for years, but never seen any new releases in the last years. Both are actually a shame. An outdated tool is usually of lower value. Promoting old tools might actually disappoint others and harm the initial trust in the software. History of Tiger In its day, the tool […]

Read more

Find Differences Between Two Daily Lynis Audits

Comparing Lynis Scan Results Lately I saw a great feature request for Lynis, to detect differences between two runs of Lynis. Wouldn’t it be great to run Lynis daily and then see if anything changes and act upon those differences? While our auditing tool doesn’t have such an option itself, it is very easy to implement something and fine-tune it to your needs. Report Lynis has two important files to which is logs data: /var/log/lynis.log /var/log/lynis-report.dat The first file /var/log/lynis.log has […]

Read more

The ultimate strace cheat sheet

Strace cheat sheet The strace utility is very powerful to learn what a new or running process is doing. Due to its diversity of monitoring options, the tool is less accessible at first. This strace cheat sheet helps with getting the best out of this tool. Normally cheat sheets come in a single 1 page PDF. In this case, we combined it all within a blog post. First section shows an explanation per area, the bottom of the post contains […]

Read more

Monitor file access by Linux processes

Process Auditing: Disk and File Activity Processes are the running workforce on a Linux system. Each process has a particular goal, like forking child processes, handling incoming user requests of monitoring other processes. As a system administrator or IT auditor, you might want to know at some point what disk activity occurs in a process. In this article, we have a look at a few options to quickly reveal what is occuring in a process, including disk and file activity. Monitor syscalls […]

Read more

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) […]

Read more

Linux System Integrity Explained: Ensure Data, Logging and Kernel Integrity

Linux System Integrity Explained From Data and Logging, up to Kernel Integrity Systems exist for one primary goal, which is processing data. Information security helps protecting this valuable data, by ensuring its availability, integrity, and confidentiality. In other words, data should be available when we need it. Then it should be properly transmitted and stored, without errors. Our last goal ensures that it is only available to those with a need to know. Many open source software components are available […]

Read more

Logging root actions by capturing execve system calls

Logging root actions Capturing execve system calls and store them in the audit log For compliance or security reasons you might want to capture all commands executed by the root user. Fortunately enough the Linux audit framework helps with capturing the right system calls and log it to the audit file. Configure audit To enable auditing, use the following commands: auditctl -a exit,always -F arch=b64 -F euid=0 -S execve -k root-commands auditctl -a exit,always -F arch=b32 -F euid=0 -S execve […]

Read more

Tuning auditd: high-performance Linux Auditing

Last updated on June 30th, 2018The Linux Audit framework is a powerful tool to audit system events. From running executables up to system calls, everything can be logged. However, all this audit logging comes at the price of decreased system performance. Let’s have a look at how we can optimize our audit rules. Performance tips Good auditd performance will reduce stress on the Linux kernel and lower its impact. Before changing anything to your system, we suggest benchmarking your system […]

Read more

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 […]

Read more

Viewing available test categories in Lynis

Last updated on April 1st, 2015Test categories in Lynis When auditing a server, it may be useful to only run a particular category of tests, like firewall related tests. In that case the –tests-category parameter can be used, together with the category name. Available categories To determine what categories are available, Lynis has a built-in parameter –view-categories which lists all available files. Most of the names are self-explanatory on what of tests they include. For more information about the included […]

Read more

Security Integration: Configuration Management and Auditing

Configuration Management and Auditing Increased strength when combining tools for automation and security of IT environments Tools like Ansible, Chef, and Puppet are used a lot for rapid deployment and keeping systems properly configured. These tools in itself are great for ensuring consistency over your systems. So what is Configuration Management? Configuration management is the art of keeping systems properly configured. Usually companies start small, which equals manual configuration. Each time a new system is deployed, it is configured manually. […]

Read more

Password Security with Linux /etc/shadow file

Last updated on September 21st, 2015Password Security on Linux Using the /etc/shadow file Linux systems use a password file to store accounts, commonly available as /etc/passwd. For additional safety measures, a shadow copy of this file is used which includes the passwords of your users. Or actually hashed password, for maximum security. An example of a password entry in /etc/shadow may look like this: user1:$6$6Y/fI1nx$zQJj6AH9asTNfhxV7NoVgxByJyE.rVKK6tKXiOGNCfWBsrTGY7wtC6Cep6co9eVNkRFrpK6koXs1NU3AZQF8v/:16092:0:99999:7::: For proper display, let’s split this up in several fields: user1 $6$6Y/fI1nx$zQJj6AH9asTNfhxV7NoVgxByJyE.rVKK6tK<truncated> 16092 0 99999 […]

Read more

PCI DSS (v3) Linux: Creation and deletion of system-level objects (10.2.7)

PCI DSS (v3) Linux: Creation and deletion of system-level objects (10.2.7) Some areas are within the PCI standard are definitely not directly clear when reading the description. Section 10.2.7 is one of them. It talks about the creation and deletion of system-level objects and specifically the ability to log them. System-level objects? The guidance in 10.2.7 speaks about malware and mentions database related items. That does not make auditing very obvious, as malware usually targets binaries. Therefore we have to […]

Read more
1234