Microsoft and Fireeye have both made similar claims and released substantial technical details.

Attribution is hard, but those two companies have a solid reputation and do not make BS claims.

I see where they claim it's a sophisticated / state-sponsored attack, but could you share where they attribute it to Russia in particular? If that's a political assessment made by the media that's one thing, but if these sourced have some sort of technical data that inherently links it to a particular nation... that's something I haven't seen.

Yeah, I think that every time someone/some org knee jerks "it was russia" without at least acknowledging there could be a variety of well funded actors interested in compromising the US Treasury [or any other target] for a variety of reasons and/or having the incentive to make it look like someone else could have done it, just pours more fuel on the attribution fire.