Hidden spot on hard drives?

Norberto Meijome freebsd at meijome.net
Thu Oct 6 07:16:09 PDT 2005


Gary W. Swearingen wrote:
> Jonathon McKitrick <jcm at FreeBSD-uk.eu.org> writes:
> 
> 
>>1.  Any idea where this info could be stored?
> 
> 
> The obvious place is the end of the first track between the boot
> sector(s) and the first partition.  But that's probably too easy and
> well-known.  As others have noted, Unix (eg, "dd") has easy access to
> all of the standard sectors of the HDD.
> 
> But I think I recall reading about some software that does some kind
> of special accesses of the disk drive, say to write to sector "#" and
> then tell the disk to mark that sector bad and use one of the spare
> sectors in it's place.  Something tricky like that that OS code
> doesn't know how do without a custom driver that understands very
> low-level HDD control.  Of course, if their software can undo it,
> anyone's could, but not if you don't know how, or maybe they've
> managed to pick the sectors cryptographically or something, making the
> job really tough.

ah yeah, i remember this one from way back when (10+ years ago maybe).

I even remember reading in a book about game development the suggestion 
to add a HUGE amount of (needless) data to the game to make it a real 
pain for the would-be-illegal-user to make a copy. That was, of course, 
before cd burners were ubiquitous and copying by to floppies 500 MBs for 
a single game wasn't a joke. (yes, ridiculous suggestion, i know)

> 
> I've also heard of copy protection moving heads half a cylinder and
> storing data "between" normal tracks, but that was probably on
> floppies; HDD tracks probably almost overlap as it is.

Where does HPA(Host protected Area) sit in all this? is this the 'boot 
sector' trick?  I've heard about it in relation to XBox, and seen it in 
some big-brand-name laptops and HDs of NAS-devices. FWIW, i don't think 
HPA is a bulletproof solution either (nothing a dd won't read / 
overwrite, as many others have mentioned).

Beto


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