Why should we even care about the academic definition of a backdoor? Is it less of a privacy problem if it is a "malware"?
No, words have meaning and we should be using the correct terminology. A backdoor usually means that the product is delivered straight from the manufacturer with a way to bypass the authentication set up by the user. By rootkit we typically mean a program that is installed after the product has been deployed and then gives the possibility to bypass authentication.
Both are bad, but one is arguably worse than the other, because one sets every user at risk, the other is much more targeted.
> what matters is that our systems are compromised by an agency
Chinese systems were compromised by an American agency. That's pretty much their job description and business as usual for a spy agency in any country. You can be outraged at that, but if the NSA were putting backdoors in the Linux kernel, then they'd put the whole world including their own citizens at risk, which is arguably even worse.
99.999% of our systems are not compromised.
So yes they do cyber attacks but the scope and method is so very different between those two categories.
Nor did I see any description of a backdoor in Linux, just a backdoor that runs on Linux.
The reason why is remains a "secret" is that the whole matter is deeply, deeply political.
We are amidst a new Cold War -this time between the US and China. The sole purpose of this backdoor could be exactly to spy on the Chinese government or corporations.
Yet we all know that the NSA would not limit the use of the backdoor to that.
The end result is he carefully picks and chooses topics for which he is passionate about (in the context of computing and 'software freedom') nearly right up and down party lines.
Once upon a time a basketball player had both a gambling addiction and a mistress addiction. No news reports on both issues due to the fact that said player controlled sports reporter access to him.
News not covered never ever has to do with politics no matter what side it has to do with access to the subject being controlled.
Aha Aha, I got the verbatim info from the sports reporter, he is now dead for over a decade, and the player I refer to is MJ of the Bulls.
Not saying these are a 100% secure but you're plying this was _built_ into Linux (and other OSes). It was not. And the PDF makes no such claim either.
Also, (2022)
Personally, I flagged it because that's very misleading and it's not a backdoor.
If anything, the original title should have been edited in the opposite direction, to not use the word "backdoor". Or to add [sic]. But "a backdoor" without "in Linux" is not super egregious.
I thought this was the working assumption.