The threat from Islamic State's 'fifth column' in Europe

Jihadi veterans have been seeking to cause disarray among European intelligence agencies with hoax attacks that distract from real ones and attempts to infiltrate public agencies and companies. As a result security official are having huge difficulties in trying to measure the true scale of the terrorist threat that faces us. In the last of this lengthy series of investigations on Islamic State's intelligence operations, Matthieu Suc reports on the dangers still posed by jihadist agents operating within Europe despite Islamic State's major reverses in Iraq and Syria.