Visible crew/equipment: A few shots after the White House and chopper are destroyed, when a light colored car lifts up from the bottom left to top left of the screen, the roll cannon is visible under the car, between the front tires. (00:52:10)
Visible crew/equipment: When the President stands by "the big tamale" he asks Dr. Okun if he can tell them anything useful about them. When Okun rushes up the ramp as he passes Nimzicki, the actor's mark is visible on the ramp, directly in front of the Secretary of Defense. (Only visible on fullscreen DVD.)
Visible crew/equipment: A couple of shots after Jasmine grabs Dylan from the car, the rears of a red car and white car are shown tossed up from a front shot. Next shot from behind, the same two cars are shown tossed up again where we can see the flat belt system between the four tires and the mechanical arm at work doing the flipping. (00:53:40)
Visible crew/equipment: After General Grey shows the nuclear missile and launch mechanism to Steven and David, when Connie asks, "Why you?", in the next shot just as a woman in a white lab coat passes David, his yellow actor's mark is visible on the floor at his feet. (Only visible on fullscreen DVD.)
Visible crew/equipment: After Russell shows up in the FA/18 with the last missile, when President Whitmore says, "We'll draw them off and it'll be all yours," the set's multiple light tower is reflected on the President's helmet visor.
Visible crew/equipment: When Russell lands his crop-dusting plane and Miguel rides up alongside on his motorbike. The equipment used to help stop the motorbike, at the right position for the close-up, is visible on the ground - but it's gone in the wideshot. (Only visible on fullscreen DVD.)
Answer: Remember that the aliens had to interface with our satellite computer code first...David simply "reverse engineered" the code to create the virus. When it was uploaded, they didn't have enough time to combat it.