Interesting...someone submitted a FOIA request to the NSA, and got a response:
Because of the classified nature of the National Security Agency’s efforts to prevent and protect against terrorist attacks, the fact of whether or not any specific technique or method or activity is employed in that effort is exempt from release pursuant to the exemption provisions of the FOIA.
We can neither confirm nor deny the existence of records responsive to your request. The fact of the existence or non-existence of responsive records is a currently and properly classified matter in accordance with Executive Order 12958, as amended. Thus, your request is denied pursuant to the first exemption of the FOIA, which provides that the FOIA does not apply to matters that are specifically authorized under criteria established by an Executive Order to be kept secret in the interest of national defense or foreign relations and are properly classified pursuant to such Executive Order.
Moreover, the third exemption of the FOJA provides for the withholding of information specifically protected from disclosure by statute. Thus, your request is also denied because the fact of the existence or non-existence of the information is exempted from disclosure pursuant to the third exemption. The specific statutes applicable in this case are Title 18 U.S. Code 798; Title 50 U.S. Code 403-1(i); and Section 6, Public Law 86-36 (50 U.S. Code 402 note).
As your request is being denied, you are hereby advised of this Agency’s appeal procedures. Any person denied access to information may file an appeal to the NSA/CSS Freedom of Information Act Appeal Authority. The appeal must be postmarked no later than 60 calendar days of the date of the initial denial letter. The appeal shall be in writing addressed to the NSA/CSS FOIA Appeal Authority (DC34), National Security Agency, 9800 Savage Road STE 6248, Fort George G. Meade, MD 20755-6248. The appeal shall reference the adverse determination and shall contain, in sufficient detail and particularity, the grounds upon which the requester believes that the determination is unwarranted. The NSA/CSS FOJA Appeal Authority will endeavor to respond to the appeal within 20 working days after receipt, absent any unusual circumstances.
http://www.shaftek.org/blog/archives/000391.html