I wish we had more concrete evidence than "according to people familiar with the matter" though. That's kind of my issue: if these attackers are so sophisticated, how can they be sure it's this particular group?
I realize that there are probably many good reasons for not sharing deep technical details in such cases, but from the point of view of an external observer it's really hard to know who should be trusted and how solid these claims are.
I realize that there are probably many good reasons for not sharing deep technical details in such cases, but from the point of view of an external observer it's really hard to know who should be trusted and how solid these claims are.