Emile Hirsch told io9
the aliens in the film are called Spooks. We don’t call them Spooks, but that’s what they will be called when the movie comes out. We don’t go: “There’s a Spook.” We don’t say that. We’re just like: “That thing!” But [they're] the Spooks, because they’re like invisible, they’re like ghosts kind-of. That was the thinking on the writers’ part, on the pen to the pieces of paper.
Images provided by slashfilm
The Darkest Hour will open in 3-D December 23, 2011.