Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds.

Armed French police patrol in Longpont, north of Paris, France, Thursday, Jan. 8, 2015.
Armed French police patrol in Longpont, north of Paris, France, Thursday, Jan. 8, 2015.

    JUST WATCHED

    Why it's hard to track down potential terrorists

MUST WATCH

Why it's hard to track down potential terrorists

CNN's Tom Foreman examines the challenges authorities face tracking down and monitoring potential terrorists.

Why it's hard to track down potential terrorists

CNN's Tom Foreman examines the challenges authorities face tracking down and monitoring potential terrorists.