reporter: katherine herridge, fox news. carley: terrorists spreading propaganda through social media apps aimed at teens. rob: the video sharing apps has millions of users. is this the new battlefront americans need to keep on their radar. carley: the national security program, tara frederick, joins us with parents need to know. the scary thing is i don t think a lot of parents know what to talk is and we are hearing isis is putting propaganda on it. reporter: the thing that strikes me is this tactic is not new. iran into this as a counterterrorism analyst at facebook and special operations forces. a different platform but the tactic is the same. what these terrorist groups do is use these new platforms to cast a wide net and narrow down your focus often moving off of