VirtualBox

VirtualBox is a program that will allow us to install machines, just like normal computers, inside our own machine. We will have one computer, and we will install other computers inside it, acting as virtual machines. These are very important in terms of penetration testing; we're going to be using them a lot in order to set up a lab. It's very important to note that a virtual machine is just like a completely separate, working machine; there is nothing we will lose by installing an operating system as a virtual machine, and it will perform just like it does when installed on a separate laptop. Basically, instead of having four or five computers or laptops around us (so that we can try to hack into them), we're going to install them as virtual machines inside our own machine. This might seem a bit vague now, but once we get further into the chapter, the concept of how VirtualBox works will become clearer.

Basically, we are going to have three computers inside our main computer. We will have the following three machines in our lab:

• Attacker machine: Kali Linux
• Victim 1: Metasploitable
• Victim 2: Windows

For example, if our main computer has macOS, we are not going to do anything with that. We have a machine that will be an attacker machine, running Kali Linux, and we will learn more about Kali Linux in a later part of this chapter.

We will also have two victims:

• A victim that runs on Windows.
• A victim that runs an operating system called Metasploitable.

So, we're going to have our own machine, and then have three separate machines inside it. This will be possible by using VirtualBox.