You make the area around a campsite appear to be a thicket of untouched and forbidding foliage, or some other unwelcoming feature matching the surrounding terrain. Creatures outside the area cannot sense any activity going on inside the area- they cannot smell campfires or cooking food, they cannot hear conversation, loud noises, or spells being cast, and they cannot even feel heat or a rush of wind coming from the area. Those inside the area can see out normally. Once a creature steps into the area of the spell, it can see everything in and around the area normally.