fib continues to warn that terror suspects have gone dark increasedly communicated through encrypted messages that's widely available, but impossible for the intelligence community to monitor. u.s. officials tell cnn that the risk of terror attacks remains very high. >> based on recent past trends isis has beenling to and able to push out information to americans, and a small number have been willing to act based on that. >> here's a worrisome development, the fbi is seeing isis exercise more control over plot here inside the u.s. for some time they've been saying these attacks are more inspired encouraged maybe even given general ideas for attack methods and targets. now, however, they're seeing some direction from isis operatives overseas including picking targets. brianna, we've been talking for a long time about the worry of foreign fighters returns from