How to solve Shellshock on Debian and Ubuntu

Protect against Shellshock For Debian and Ubuntu Shellshock is a serious software weakness, or vulnerability, in Bash. This shell is used on almost all Unix based systems, including Debian and Ubuntu. As it can be used without much efforts and remotely exploit systems, it has a maximum vulnerability score according to CVSS. Upgrade Bash First update the software repository with apt-get, using the update parameter. apt-get update && apt-get install –only-upgrade bash Your system should now have a newer version […]

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Creating audit trails – Logging commands on Linux with Snoopy

Creating audit trails Logging commands on Linux with Snoopy Our customers often want to set-up an audit trail for accounting purposes. When something happens, they want to be able to see what happened, when it did and by whom. Defining an audit trail is also becoming mandatory for compliance, like PCI. One possible solution we cover is using Snoopy, a small library to log executed commands. How it works Snoopy is a wrapper around the execve() function. This is a […]

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Linux Security Scanning for Dummies

Linux Security Scanning for Dummies Every system needs some level of protection. Still, many people simply forget to do it, or can not find the time to properly do it. To be as efficient and effective as possible, let’s take at a structured way for security scanning your Linux machines. The 5 dummy steps are: 1. Focus on risk Like not every company is a bank, our systems are not all part of a top secret mission. We have to […]

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Linux security: Reviewing log files

Linux security: Reviewing log files Log files are the precious collection of system events. Still many people don’t use them, until it is really needed. Let’s go from the reactive use of log files to a proactive stance. The Logging Dilemma Capturing events helps in troubleshooting. By defining what events are ignored and which ones are logged, we get a quick overview on the status of a system. The dilemma is usually in how much logging is enough to get […]

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How and why Linux daemons drop privileges

How and why Linux daemons drop privileges In this article we have a look at the privileges of Linux daemons and dropping privileges in particular. The samples provided are in C. Why drop privileges? Some daemons need root permissions to start. This happens for example when a daemon wants to bind to a low port (<1024). However running network based daemons with root permissions is considered to be a serious risk. In case of compromise of the process, an attacker […]

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Security Audits – How to Prioritize Audit Findings

Security Audits – How to Prioritize Audit Findings Technical audits or vulnerability scans will reveal a lot of findings. They can be overwhelmed and forcing the reviewer to freeze, not knowing where to start. To overcome this issue, we should prioritize the findings and determine the consequences of each finding for our company. While an open directory listing on a web server might in one situation not be preferred, it would make sense for others. It is the context which […]

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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 […]

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How to audit AIX Unix systems with Lynis

How to audit AIX Unix systems with Lynis Each system is as strong as its weakest link. Also for systems running on AIX this rule applies. Therefore a regular audit can help finding the weakest links. Next step is then the fortification of these weakened areas and implementing system hardening measures. What to audit? There is a lot to look for when auditing a system running AIX. Let’s have a look at the most important areas. File systems Monitor alterations […]

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