Hm… I do kind of get what you’re saying now. I just don’t agree with this limited way of applying the term. I do know what a backdoor is, yes.

So: If you have a remote shell program like sshd, it can do what it does. There might be malicious code inside, there might not. But if we said specifically that it had a “backdoor,” that would mean that it can also accept arbitrary login requests (bypassing the normal authentication) for someone to log in and run arbitrary commands. That’s a backdoor. The code’s still running within the context of the terminal program, but what makes it a backdoor is that it’s doing it on demand from some remote user. Yes?

If you had a social media program like Tiktok, it can do what it does. There might be malicious code inside, there might not. But if we said it had a “backdoor,” that would mean that it can also execute arbitrary code (bypassing the normal authentication of downloaded apps) for someone to run arbitrary code. That’s a backdoor. The code’s still running within the security context of the app, but what makes it a backdoor is that it’s doing it on demand from some remote user.

There’s another related definition where “backdoor” means a secret way of escalating privileges, but that up above is the context where I’m using it, which is also consistent with Wikipedia’s definition. You’re free to not agree with my definitions, I don’t wanna argue any more than you do and I’m happy if you want to use the word however you want. But that’s how I see it.