I am not sure what you mean. Do you mean VirtualBox or the VMs made with
VB? The second is easy. You can clone and existing VM in the VB menu at
Machine, Clone. You can also save the state of a running VM and restore to
that point. Go to Machine, Take Snapshot. I find this useful for Windows.
There is no need to use AV or other things that will slow your machine. I
just clone take a snapshot and then run the snapshot if I get infected.
That has not happened yet, though. Touch wood.