These fortress-like AT&T buildings are central to a secret NSA program that has monitored billions of communications, documents and sources reveal.
Stephen Budiansky, in his book, Code Warriors, explains how the pre-cursor to the NSA tape recorded communications prior to and during WW II. As they worked to decrypt and interpret contemporary messages, access to older communications proved invaluable to understanding current events and why enemies were making the decisions they were making.
In a similar way, the NSA records and stores large quantities of communications in the event that a future situation will benefit from analysis of past communications. For this reason, the NSA built enormous data centers, such as the NSA Data Center near Provo, Utah, specifically to store enormous quantities of digital data including phone calls, radio signals, text messages, emails, and general Internet data traffic. Much of this data collection may never be accessed – except in time of national emergencies or war.