Evidence that the NSA was secretly building a vast database of U.S. telephone records - the who, the how, the when, and the where of millions of mobile calls - was the first and arguably the most explosive of the Snowden revelations published by the Guardian newspaper in 2013.
Up until that moment, top intelligence officials publicly insisted the NSA never knowingly collected information on Americans at all. After the program’s exposure, U.S. officials fell back on the argument that the spying had played a crucial role in fighting domestic extremism, citing in particular the case of four San Diego residents who were accused of providing aid to religious fanatics in Somalia.
