U.S. Treasury says its computers were hacked by a Chinese 'threat actor' in a 'major incident'

[erronis]

7. As dlk says below, "We'll never know"

Even if the US authorities (FBI, CISA, etc.) do uncover some of the traces of the infection, it will not be disclosed to the public.

1. You don't want your adversaries to know what you have uncovered;
2. The public has no right for full disclosures. (sarcasm)