information being intercepted and unless you subscribe to the channel, you wouldn't even know about it. >> telegram is it a free app that isis uses to spread its propaganda and recruit new members. it's also a way that isis can secretly wire money or carry on private text messaging. >> so i'm going to say, "hello" and send. so it's just like a conversation. >> since the attacks in paris, telegram has taken action blocking hundreds of isis channels. it's a step, but private encrypted messaging between members has not been affected. for u.s. intelligence officials, encryption is of grave concern. but to privacy activists, it is a necessary reaction to the kind of mass surveillance programs former nsa staffer edward snowden revealed. >> end mass surveillance. >> director james clapper says that snowden's likes have irreparably harmed intelligence