<human>:  When did the NSA start collecting data on Americans?
<bot>: The NSA started collecting data on Americans in the late 1990s. The PRISM program is an internal NSA program that allows the agency to collect data from many of the biggest tech companies, including Google, Facebook, Apple, Microsoft, and Yahoo. The NSA claims that the PRISM program is legal, but many people believe that the program is unconstitutional and violates privacy rights.