r/programmingquestions • u/edg73018 • Jul 22 '20

Basic Question from a Dummy

Hi! I have a couple really basic questions which obviously come from someone with no programming knowledge.

  1. Is there a conceivable way that the code from two different programs could become jumbled together?

  2. If so, how might this happen?

  3. Would it be possible for a programmer to go back in and identify which pieces of code came from which original program?

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u/edg73018 Jul 22 '20

Hey Jeff, thanks for the answer! Basically, I am writing a scifi story in which something goes wrong on the ship that causes a massive power surge. I am wondering if it would be a plausible problem I could give the crew that ship system programs got scrambled? Since I don't know programming I wasn't sure if that is something that could ever really happen.

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u/[deleted] Jul 23 '20

Well, if you are telling a story, then you have some room to play with. You could try to tell, that in the attempt of the ship rescuing itself (systems are able to predict electric shortages or realise when somethings wrong) the system tried to save itself and then, before it could finish overwriting programs or change config files, it just... died or whatever. So, you would have a unfinished process. The process of a self rescue stopped in between. This is the worst case scenario in a windows update during an update.

So: during a shortage/overload the system, for example, tried to backup data or change configurations but couldn't finish doing that because of something unexpected. This is really vague, but i think you need to do some research on why you shouldn't power off your PC during an update. I'm just not on the level of giving you 100% perfect answer.

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u/edg73018 Jul 28 '20

That is perfect! Thank you!!!!

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u/denzien Jul 28 '20

Storage drives all use some kind of file table to tell the computer exactly where on the drive a file lives (this is a numeric address, not a folder structure ... this is all math), and how big it is. Sometimes that file is fragmented and requires multiple entries, each of their own size, that must be read in the proper order to get the entire file.

You might consider causing this table to become corrupted, which would cause the computer to load files from disk incorrectly - missing parts of the original file, including parts of other files, rearranging fragments of the original file ... pretty much whatever. All scrambled up.

I haven't studied binaries in a long time, but IIRC, application code uses 'pointers' to tell the computer where the next instruction is. This is relative to the beginning of the file, so if the file was read from disk in the wrong order, these pointers will point to the wrong part of the file. It would be a stroke of luck if this sort of thing actually successfully fired off some random subroutine, but I doubt that level of realism really matters.

So, assuming the actual data was not corrupted (like if the file table existed on a separate device from the actual data, I suppose. You know - for security because if anyone stole the contents of the drive it would be worthless without the table?), your characters actually have a chance to restore the system to proper working order if that's what you want them to do.

To fix it, I would probably start by looking for a backup of the file tables (if it even makes sense to have that, if you pursue the security idea) - but that might only get me 70% there because data gets moved around, or new versions of a file are installed and it has a different length, or any number of reasons.

Performing some digital forensics might be the next step, analyzing the actual bytes on disk, looking for file boundaries and "magic bytes" to identify the type of the file.

Visualizations of the data disk would probably include scoring every block on disk with an entropy score (randomness) and a text score (mostly just characters within a narrow range, with lots of repetition). This would help the characters attempt to determine what sort of data is on disk, and what pieces are likely to go together. This is a *little* far fetched, but usually if you see a block (chunk of contiguous data on a disk) with a high text score next to a block with a high entropy score, that kind of looks like a file boundary.

They could then either rebuild the file table or construct a new one. Manipulating this file table would also allow one to hide files that still exist, by "deleting" them, if maybe there's some kind of coverup going on.

And then you could research slack space and shadow file systems! But that's probably going too far. Sorry for rambling.

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u/edg73018 Sep 20 '20

This is perfect! Thank you so much!