In this section, we will install a vulnerable virtual machine as a target virtual machine. This target will be used in several chapters of the book, when we explain particular topics. The reason we chose to set up a vulnerable server in our machine instead of using vulnerable servers available on the internet is because we don't want you to break any laws. We should emphasize that you should never pentest other servers without written permission. Another purpose of installing another virtual machine would be to improve your skills in a controlled manner. This way, it is easy to fix issues and understand what is going on in the target machine when attacks do not work.
In several countries, even port scanning a machine that you don't own can be considered a criminal act. Also, if something happens to the operating system using a virtual machine...