The hypervisor networking

In our lab, we are going to be using two networks within VirtualBox: a NAT network and a host-only network. Our Kali box will be connected to both the networks, so it can communicate with devices on the internet, download updates, and get software packages as needed. Our target machines will only be connected to the host-only network. The host-only network can only talk within the host and among other devices connected to the host-only network. It cannot communicate through your Ethernet or wireless networks. This setup is extremely critical to our testing environment, as we do not ever want to expose our testing hosts to the outside world, as they are very vulnerable and will be hacked rather quickly.

To further protect the networks that your lab is connected to, we would actually suggest disconnecting the virtual adapter of the Kali virtual machine that connects to the NAT network, unless specifically required for the recipe operation. This way, your network is protected from accidental exposures to any attacks you may be sourcing from Kali.