In the closing credits of Citizenfour, Poitras took the unusual step of adding an acknowledgment of the free software projects that made the film possible: The roll call includes the anonymity software Tor, the Tor-based operating system Tails, GPG encryption, Off-The-Record (OTR) encrypted instant messaging, hard disk encryption software Truecrypt, and Linux. All of that describes a technical setup that goes well beyond the precautions taken by most national security reporters, not to mention documentary filmmakers.