A method of active detection of at least one threat to the homeland security. Each such threat is either hidden inside at least one cargo container before transit, or is placed inside at least one cargo container while in transit; each such threat while interacting with its surrounding generates a unique threat signature. The method comprises the following steps: (A) substantially continuously probing each cargo container; (B) detecting at least one threat signature; (C) processing each detected threat signature to determine a likelihood of at least one threat to become a threat to the homeland security; (D) identifying at least one container that includes such threat to the homeland security; and (E) eliminating such threat to the homeland security.