I was looking for a tool to scan my internal and external network devices for vulnerability scanner. I found and installed "OpenVAS" which is available as a Virtualbox image on my Virtualbox host machine. So far I am very satisfied with the results. Although I did not found big issues with my machines, I will run that tool now on a regular basis to make sure that there is no know security issue in future.
OpenVAS is a framework of several services and tools offering a comprehensive and powerful vulnerability scanning and vulnerability management solution. The framework is part of Greenbone Networks' commercial vulnerability management solution from which developments are contributed to the Open Source community since 2009.
The actual security scanner is accompanied with a regularly updated feed of Network Vulnerability Tests (NVTs), over 50,000 in total.
All OpenVAS products are Free Software. Most components are licensed under the GNU General Public License (GNU GPL).