to prevent a virtual image from connecting to outside networks e.g. to download updates the following network setting can be selected:
when selecting “host-only” the virtual machine is not able to connect outside networks.
If the virtual machine should be able to connect to outside network the following option should be selected:
when selecting “NAT” the virtual machine is able to connect outside networks, traffic from outside network is not allowed to connect to services inside the virtual machine.
using the Option “Bridge” also allows traffic from the outside network to connect to services inside the virtual machine.