Every article I have read on backdoor attack prevention says pretty much this:
Protecting against them may be difficult.
I am tired of reading how it can be ~difficult~ to protect against. Difficult is a fuzzy word. I want to know concretely, yes or no. If you can protect against them or not. Wondering if one could answer yes you can protect against them, or no ultimately you cannot, along with a brief reason why. I don't care that it is difficult, I would prefer to know if there is anything possible to implement to be secure.
I am pretty sure there are a class of things that are completely unprotectable, such as firmware updates which may insert undetectable code below the operating system. So it would be good if the answer could be divided into two sections, the things that can't be protected against (firmware updates which may inject malware), and things that can be protected against at the boundary of all possible things to protect against. That is, there's a huge amount of things you could protect against, so outlining them all is way too much. But there is probably a very small amount of things right at the edge of the most difficult to detect things. I would like to know what those things are that are extremely difficult to detect, yet are still 100% detectable. I don't want to know about the things in which ~you might be able to detect it~ or ~it is difficult to detect~. Only if it is guaranteed detectable, given enough knowledge, the things at the edge of difficulty. Things in which it would take millions of computation-years to break like password hashes are considered undetectable for this post. I am only wondering about things in which, if you are educated enough, you could detect in a matter of a few months of work or something.
Another example of how this is confusingly presented is this:
Generally if they’re a good hacker, you never will know. One of the only ways to know for sure is to use another computer to “sniff” the network traffic coming in and out of your computer to see if there’s anything that seems out of the ordinary.
To me that says:
You cannot detect it if they are good. But you can still detect it.
That is, it's an oxymoron.