datahoarder
Who are we?
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
We are one. We are legion. And we're trying really hard not to forget.
-- 5-4-3-2-1-bang from this thread
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My guess would be that it's stored in some kind of non-volatile memory, i.e. EEPROM. Not sure if anyone ever tried that, but with the dedication of some hardware hackers that seems at least feasible. Reverse engineering / overriding the HDD's firmware would be another approach to return fake or manipulated values.
I haven't seen something like that in the wild so far. What I have seen are manipulated USB sticks though: advertising the wrong size (could be tested with h2testw) or worse.
I've bought used / refurbished (not sure which) with erased smart data. It being all zeros was a clear sign of erased / tampered info. After running badblocks some relocated sectors showed up.