I have no idea how they can track or stop them IF they know who they are. My statement was based on reports I heard on TV with a politician who is on the intelligence committee who was explaining one reason we need to use air strikes. He stated that they knew there were these Americans (traitors) who are working and training with ISIS and that is one reason they need to be stopped in Iraq and other Country's because the plan IS to bring their war to this Country. How much of what he said is true, I have no clue but we know that Americans (traitors) are helping the other factions who are trying to kill us so why wouldn't they be going there to help ISIS? Makes sense to me.