WarGames (War Games) (1983)

High school student David Lightman has a talent for hacking. But while trying to hack into a computer system to play unreleased video games, he unwittingly taps into the Department of Defense's war computer and initiates a confrontation of global proportions. Together with his girlfriend and a wizardly computer genius, David must race against time to outwit his opponent and prevent a nuclear Armageddon.