The first sense of today's term is clearly the opposite of infiltration. The second sense is more problematic. It may simply be an unfortunate generalization of the first (unfortunate, since an infiltration applies only to people, not objects). However, it may also have sprung from the non-military meaning of exfiltration: "The action or process of filtering out." Since both senses are used in military contexts, my vote goes to the generalization theory.