Lynis is a security auditing tool for the Linux, Unix and Mac platform. Being open source and free to use, it is an accessible and great solution to perform security scans. Within just a matter of minutes, it displays the weaknesses in your defenses, and tips for improving them. While Lynis was initially an auditing solution, version 1.6.1 brought a very exciting new pentest option (--pentest). It allows to perform a non-privileged scans, so root access is not longer needed. Great for pentesting and to determine if there are other holes to exploit.
This tool is the result of 7 years of development and much feedback by the community. Now it supported by the original author and his company, development is active and regular updates are being released. The author also stated Lynis would remain free and open source. His way of giving back to the community and make sure nice tools do not get behind a paywall.