In the lab it's difficult to generate 400Gb/s traffic. From my perspective it seems like this attack is pretty sophisticated and has access to some pretty fat

In the lab it's difficult to generate 400Gb/s traffic. From my perspective it seems like this attack is pretty sophisticated and has access to some pretty fat pipes. It's hard to imagine that this scale of attack could come from some infected PCs. Can an expert weigh in here on the difficulty of generating this much traffic in an attack?