My point was that it's unlikely that you're dealing with malware so sophisticated that it can successfully corrupt any given OS disk image and/or fake-out a checksum verification on same -- and if it can, you're probably screwed anyway.
That's one little thing about HN -- most people are so literal, completely missing the point.
I'm sure that it's not (yet) possible to do that, although that would be a huge breakthrough. Imagine malware that could detect what (OS) is on the ISO image and inject itself into the files inside the ISO stealthily... all at run-time when you click the "burn this ISO to this CD" button.
My point was that it's unlikely that you're dealing with malware so sophisticated that it can successfully corrupt any given OS disk image and/or fake-out a checksum verification on same -- and if it can, you're probably screwed anyway.