This has to be a very scary thought. As if Cyber Warfare weren't scary enough. And, as with the latter in certain situations, this could be a two-pher for whichever antagonist that wanted to employ it. Not only does it serve to potentially bog down so many critical service delivery systems (as well as sow fear and desperation among the populace), it provides a new source of income to further advance the goals of said antagonist.
And because the entire globe seems hell bent in the race to find the absolute "Heart of Darkness" (that point of ultimate brutality that will crush all other enemies will to fight on), why wouldn't any, or even all, players in global conflict consider using it.
Such a horribly dark mentality won't be stopped by any political, or economic change alone, mine included. For that we have to look inside ourselves and decide on what we are willing to sacrifice to reestablish loving, moral principles as a way of life. In this the answer to the question of "How do you stop terror as a weapon," is to simply live the life of your ideals as much as possible. The main principle being that the only way to fight one concept of a way of life is to live a better concept of same; knowing that there will be a great deal of pain along the way.
We also need to remember that we don't need to love the ones who inflict this pain. To be angry at them, and their inhuman stupidity is perfectly human. What we do need to do, however, is to not give up on love itself along the way; even as we embrace our grief and mourn the ones we may lose in the process. Keeping faith with love, for the sake of loving life is what is at stake here; working through the needed grief and then boldly loving again, and again, and again.
The simple fact of the matter is that we will win nothing of value in trying to defeat them by becoming more brutal than they are. It might well leave one group still standing, but upon what, and for how long, is the real issue.