Surveil coalition troop movements. though drones are inexpensive and accessible. isis propaganda videos encouraged drone attacks worldwide and now some experts question whether the u.s. is prepared for that. >> we don't have this type of technology, both the detection and countermeasure technology, in place yet. >> the use of drones by terrorists is fueling a counter industry. dozens of companies have started up, like drone shield, which offers a drone gun, a signal jammer, or allows the operator to land safely. too small to detect on radar, drone shield can detect them by sound. >> we listen ...