We all know that Bitcoin is also popular to criminals because they can use it without exposing their identity. It will be more convenient to them to use Bitcoin so that they can hide their identity. Do you think that terrorist groups like ISIS use it for their transactions?
I think they are using it I have heard a story that anonymous are hacking their bitcoin in the deepweb ,
I don't think if that's true or what but I strongly believe that they are already using it because as long as they could use it as a payment for their transaction they would use it.