The Aspen Security Forum, a conference series that has become a fixture on the national security calendar, last week travelled abroad for the first time, to London. Twitter and social media at large found itself in the crosshairs of frustrated security professionals. Mark Simmonds, a former MP and now CEO of the Counter-Extremism Project, spoke of Twitter as "the gateway", and that it "needs to do much more" to clamp down on the 46,000 accounts linked to IS.