It isn't proof, but the CIA would have to emphatically say that they had human intelligence of a traditional nature that the Russian govt was involved. Not proof, considering the CIA's general record, but at least worth considering.

But they didn't do that, and only ever said "they thought" or "it looked" like Russian hacking. Which means nothing. Even worse, attributing a hack to an entity without human intelligence is setting oneself up for a bigger mistake than the Iraq war. There is no way to positively identify the perpetrator of a digital hack through digital means. Period. Even if you have access to all the routers via backdoors, as the NSA is rumored to have, and you do manage a high degree of confidence in the resulting physical origin (which still isn't 100%) you still don't know who was behind the keyboard, or even if someone didn't just load the attack on a USB stick and get it plugged in to a machine at that location.

With a bit of effort, it is also possible to copy another entity's MO, and even make the attack origin fit.

The attack was perpetrated via email phishing. I don't doubt that the malware payload was of Russian origin, and possibly even was hosted in Russian territory. It is even likely that entities that are affiliated with, and at times work with the Russian govt were involved.

The problem: Anyone with a few grand, and knowledge of certain darknet message boards could pull off the same thing. A bit of bitcoin or prepaid cards can get you access to pretty much any malware, hack, or botnet.

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I'd say that there is still about a 50/50 chance that Putin was involved. After all, he blamed Hillary for meddling in Russian elections a few years ago. So the idea that Putin would order it, or at the least look the other way, is pretty high. But it isn't proof.

Also, in this case, the accusation mainly seems to have stemmed from the security firm Counter Strike and not US agencies, and never a word from NSA. Counterstrike was brought in by the DNC, and were the ones to point the finger.

This doesn't seem good enough to start impacting relations with powerful countries, and in fact would, and has, set a dangerous precedent.

Of course, the root problem in all of this is the fact that our intelligence agencies have, by their own incompetence and dishonesty over the years, made their musings and pronunciations suspect.

Any agency that can say "yep, looks like Iraq is building nukes" can say, "yep, those contractors (that we also use/work with) who say that hack looks like Russians have a good case. it's probably Russians"

For who could be free when every other man's humour might domineer over him? - John Locke (2nd Treatise, sect 57)