Spielberg's film, which will be conceived as an investigative thriller, will be backed by DreamWorks, the studio Spielberg founded in 1994 with Jeffery Katzenberg and David Geffen.
In the book, Leigh and Harding document Assange's turbulent life from his childhood through the creation of WikiLeaks in 2006. The book goes into detail of the events of last December, where more than 250,000 secret diplomatic cables were released.
Along with Leigh and Harding's book, DreamWorks has secured the rights to another book, inside WikiLeaks by Daniel Domscheit-Berg, Assange's former colleague.
Mike Fleming of Deadline Hollywood was quoted in The Guardian saying, A good template for what they are thinking is The Social Network, where Aaron Sorkin not only used the Ben Mezrich book The Accidental Billionaires as a resource, but gathered actual testimony from the lawsuits filed against Mark Zuckerberg that detailed the formation of Facebook and provided high drama. That allowed the film to be made without a rights deal from Zuckerberg.
It has yet to be announced who will play the role of Julian Assange.
Alex Gibney is also working on a documentary about WikiLeaks. He is an award-winning film-maker who directed Enron: The Smartest Guys in the Room.