AdvertisementSKIP ADVERTISEMENTYou have a preview view of this article while we are checking your access. When we have confirmed access, the full article content will load.The disclosure comes amid congressional scrutiny and a Federal Trade Commission crackdown on commercial data brokers.The letter by the National Security Agency, obtained by The New York Times, is the latest disclosure to highlight a legal gray zone on privacy.Credit...T.J. Kirkpatrick for The New York TimesCharlie SavageCharli...