I am using VirtualBox: where the guest is an Arch ISO and the host Windows/Cygwin or a generic Linux. For sharing host folders, VB native shared folders is not an option (since the setup requires often a reboot of the ISO).
I am turning to NFS, where the VB host is the server, which does not require a heavy setup on the Arch ISO guest.
I might use the VB host-only network and restrict NFS host access only to the IP of the guest ISO, which I can predict easily when there is a single VM, or I can limit the shared folder access to the VB host-only subnet.
I wonder which are the possibilities of spoofing the IPs, allowed to access the NFS share, on behalf of other boxes sitting in the same (sub)net of the VB host.