If you want to do a thorough system security audit on a Linux machine what do you use? Cobble together a few of the pre-installed tools? Search through the numerous locations for a tool that might give you enough information to determine if your system is safe? Or, do you open up a terminal window and use the Lynis security auditing tool?

Buck-Security is a security scanner for Debian and Ubuntu Linux. It helps you to harden your system by running some important security checks. For example, it finds world-writable files and directories, setuid and setgid programs, superuser accounts, and installed attack tool packages.

Nmap (“Network Mapper”) is an open source tool for network scanning and security auditing. This intro gives you some basic and interesting Nmap usages with examples on a GNU/Linux system.

Linux security may seem daunting, but there are a host of best practices to simplify the maze. Recently, Steve Grubb of Red Hat Inc. outlined some important security principles, including minimizing admin access, the increasing sophistication of SELinux and the importance of auditing systems.

Have you ever come across a situation where you've needed a tool but didn't think you had the right one to get the job done?... Now shift into the application security mindset and voila, there's Firefox Web Developer: an unlikely "security testing" tool but one that serves the purpose very well.

Network Security Toolkit is one of many live CD Linux distributions focusing on network monitoring, analysis, and security. NST was designed to give network security administrators easy access to a comprehensive set of open source network applications, many of which are among the top 100 security tools recommended by insecure.org.

Organizations of all sizes need to mitigate the risk of insider threats. Misconduct by authorized users represents a grave threat to an organization. According to the 2005 Computer Security Institute and Federal Bureau of Investigation Computer Crime and Security Survey, organizations reported that computer intrusions from inside sources accounted for nearly half of all incidents.

Skipfish is an active web application security reconnaissance tool. It prepares an interactive sitemap for the targeted site by carrying out a recursive crawl and dictionary-based probes. The resulting map is then annotated with the output from a number of active (but hopefully non-disruptive) security checks.

Enhance regulatory compliance and troubleshooting through detailed auditing, logging and real-time monitoring of UNIX/Linux user activity.