That's about right, but the NSA also is tasked with protecting the U.S. against other nations intelligence apparatuses. For instance NSA is tasked with produci

That's about right, but the NSA also is tasked with protecting the U.S. against other nations intelligence apparatuses. For instance NSA is tasked with producing (and now reviewing for approval) cryptographic schemes to protect government and national secrets, and in general devising new ways to conduct electronic intelligence so that they can devise countermeasures for the U.S. to use. If you've ever heard of TEMPEST fonts, that's just one example.