It is unlawful for the director or any of the director's officers or employees to use for personal benefit any information which is filed with or obtained by the director and which is not made public. The director or any of the director's officers or employees shall not disclose any such information or the fact that any investigation is being made except among themselves or when necessary or appropriate in a proceeding or investigation under this chapter. No provision of this chapter either creates or derogates from any privilege which exists at common law or otherwise when documentary or other evidence is sought under a subpoena directed to the director or any of the director's officers or employees.