(b)(7) EXEMPTION 7 (D) Identity of a Confidential Source. This exemption provides protection for "records or information compiled for law enforcement purposes [which] could reasonably be expected to disclose the identity of a confidential source --including a State, local, or foreign agency or authority or any private institution which furnished information on a confidential basis--and, in the case of a record or information compiled by a criminal law enforcement authority in the course of a criminal investigation, or by an agency conducting a lawful national security intelligence investigation, information furnished by a confidential source."