Given that most characteristics of binaries can be spoofed and seeing from the CIA documents published on Wikileaks that at least that organization is cautious to deploy several methods such that their malware cannot be linked to each other and cannot be linked to the US, how is APT attribution done?
As APTs are said to repurpose and recycle code and binaries found in the wild and given it's easy to throw in some comments in a different language or character set, I don't see how attribution of campaigns to APT groups and groups to state sponsors works.
Keeping in mind that some states actions are aimed at confusion and discord in other countries and the political impact and reason behind attacks or publications is often not clear nor foreseeable:
What are ways to attribute a specific sample to an APT group and how can such a group be associated with a state sponsor?