I have said before, "any protection the human mind can conceive of, another human mind can find a way around" so there is no absolute security.
That's the answer I was expecting, and it's a good one.
And it suggests to me that it might be wise to wait a while before jumping on the APFS bandwagon, either by avoiding High Sierra altogether or by running it on a SSD formatted HFS+ (which I believe is possible).
