"Fingerprints" is very vague and hand-wavery.
Those who track the various APT groups do track the modus operandi, coding techniques, etc.
It is true a new successful hack does need some novelty and "outside of the box thinking", but a complex hack, and especially a persistent one, can't be completely new from the ground up - it would take too much time to plan and build.
Nor you suddenly appear on the scene with something very sophisticated - hackers have to learn their "job" too, and in states were surveillance works far better than in others is more difficult not to get into the radar in your early stages - and maybe "advised" what is is "best" for them. Capable hackers may even be recruited by already established groups with the "right" ties and contacts.
Biting the hand that feeds IT
