I have read the now unsealed March 6, 2018, indictment against Julian Assange for conspiring with Chelsea Manning, and one part of it says that "Manning copied a Linux operating system to a CD, to allow Manning to access a United States Department of Defense computer file that was accessible only to users with administrative-level privileges." Other parts of the indictment says that Manning used a Linux operating system to gain access to a "hash file" of someone else's password.
I don't want to presume too much about how incredible this scenario is. I have Ubuntu Linux on my laptop, and it does not turn me into a superspy, but are we talking about some obscure version of Linux that is used to access files in a way that I am not aware of? Can anyone speak to this?
Linux can access almost any file system; I am not an expert, so I do not know if there are any file systems that Linux cannot access.
For example, you can boot any system - even if it has another operating system installed on it - from a bootable USB stick or CD. Once booted, Linux can be used to mount and access any physical drive that was already in the system - or, for that matter, any drive you wanted to put into the system whatever file system (or not) is on that drive. You would be able to read/write/erase files on that/those drive(s). If the files are encrypted, then that might not be of much use, but that is the only limit to the process.