[l0new0lf-G]

There is a link to a PDF with technical details right in the beginning.

[Dylan16807]

I read it and didn't see answers to any of that.

Nor did I see any description of a backdoor in Linux, just a backdoor that runs on Linux.

[mr_mitm]

In western infosec circles, the term C2 framework (command and control) would have been more appropriate.

[GartzenDeHaes]

So there is. I guess the backdoor is distributed through malicious PDF's.