In Pics: Inside the US National Security Agency 5 Photos . Updated: 11 Jun 2013, 12:32 PM IST Livemint Since PRISM was first revealed by whistle-blower Edward Snowden, there has been much discussion around the US National Security Agency's top-secret program and the agency that runs it. A look at the NSA. 1/5The National Security Agency (NSA) headquarters at Fort Meade, Maryland. The revelations about the National Security Agency’s domestic surveillance activities, and its top-secret program PRISM has brought it under the media glare. AFP 2/5PRISM is an electronic surveillance program and has been operated by the NSA since 2007. It is a codename for a data collection effort and has been designed by the national security program designed to sniff out terrorists. AFP 3/5Whistle-blower Edward Snowden, in picture, leaked the documents in June 2013, showing that the data obtained under PRISM allegedly includes email, videos, photos etc. Snowden, an NSA worker for past four years, admitted his role to The Guardian. AFP 4/5NSA’s Threat Operations Center. The leaked documents identified several technology companies like Microsoft, Yahoo!, Google, Facebook, YouTube, Skype and Apple as participants in PRISM. The companies have denied the allegations. Reuters 5/5A video wall display at the NSA. US President Barack Obama, defended the NSA’s surveillance programs, branding them legally authorized and helpful to prevent terrorist attacks. Reuters