Hard drive modifying data in flight (was: Free 500 USD laptop proposal)

[Ben Finney]

"Neal H. Walfield" <neal at walfield.org>
writes:

> At Sun, 23 Nov 2014 23:39:09 +0100,
> Paul Hänsch wrote:
> > I don't get this point:
> > 
> > ""quote --
> > - 128 GB SSD (this would be the one component that might have to be 
> > proprietary as I’m not aware of another option)
> > -- ""
>
> Don't trust a hard drive to not modify the data in flight:
>   http://spritesmods.com/?art=hddhack&page=5

I've now read that (short) page, but it doesn't say anything to me about
“hard drive […] modify the data in flight”. Probably because I'm not
expert on hardware hacking.

Can you point to, or write, an explanation of what a free-software
proponent is expected to learn from the above page?

-- 
 \        “The restriction of knowledge to an elite group destroys the |
  `\                   spirit of society and leads to its intellectual |
_o__)                                impoverishment.” —Albert Einstein |
Ben Finney