Director Laura Poitras edited the film in Germany after flying directly there from Hong Kong with the Snowden footage, to prevent the FBI from showing up with a search warrant for her hard drives.
Edward Snowden used the number "4" for his code name because Thomas Drake, William Binney and J. Kirk Wiebe all tried to expose the NSA's mass surveillance before him; in his mind they were numbers 1-3.
According to an undisclosed source in the film, 1.2 million people are on watch lists of the US intelligence agencies.
Laura Poitras took many security precautions related to the film, described by military writer Peter Maass among others. She moved to Berlin, Germany after being detained repeatedly at border controls when entering the US. She edited the film in Germany after flying directly there from Hong Kong with the Snowden footage, to prevent the FBI from showing up with a search warrant for her hard drives. All the film footage is kept on encrypted drives with multiple levels of nested protection. The computer she uses for reading sensitive documents is separated from the internet by an air gap.
Before coming out as a whistle-blower Edward Snowden had researched previous cases of leaks in NSA by Thomas Drake, William Binney and J. Kirk Wiebe extensively to try and avoid being silenced and having his life destroyed for even considering speaking out.