I have also been a designer for many years (my company is 44keys.com), and had the great opportunity to work with David Fincher, Carrie Anderson Smith, Peter Mavromates, and Alex Olivares doing design and VFX work on this film. 

All computer screens in the film are shot green screen and the screens are added later.  I designed and composited many of these screens, working with this incredible editing team (that would go on to win the Academy Award for Film Editing for this).