Re: That was believeable until the "grammatical mistakes"
That's right - only Russian is written in Cyrillic, those investigators have nailed it. And all Russian hackers are direct employees of Vlad.
Last October ISIS released video of a group of Kazakh children training with them, along with accurate subtitles in Russian and English. And recently it was reported that the commander of Tajikistan's special forces defected to ISIS.
Other languages that use Cyrillic and have significant populations throughout the Russian Federation: Chechen, Chuvash, Uzbek, Tajik &c.
Might it be that someone from one of these communities might have orchestrated this? The sanctions on Russia are hitting these communities a bit harder than anyone else so perhaps there is further motivation?
But then I keep forgetting that it is the belief of the security services that supporters of ISIS are obviously ignorant benighted idiots who struggle speaking one language.