Horror films, as Hollywood knows, have a grisly fascination and when the horror is real, the fascination is all the greater. With its graphic atrocities, its slave markets, its professionally-made films of gruesome beheadings and mass public executions, the jihadists who now call themselves Islamic State know just how to push our buttons. And that, of course, was their plan. But while the script seems to be written by Genghis Khan, the means they employ are ultra-modern.  IS  has become the leading purveyor of fear and dread but it uses Twitter and Facebook to reach us. Middle East expert Abdel Bari Atwan explains exactly how IS propagandists and recruiters use the necromancy of the “dark web” to overcome our attempts to stop them. In this baffling and dangerous wild