War Zones are the mission icons that are brown/dark orange with a white icon and border. They will be a threat sector or drop zone. There isn't anything on the mission map that says war zone despite the developers previously making it sound like war zones and drop zones were different activities. Drop zones are usually pretty fast, especially ones in Utah. You will have to set the difficulty to Challenge III each time before starting the mission. They are pretty easy. It's just a bit time consuming to do 30 of them and the drop zones don't have as much gear drop as a threat sector.