WarGames

A young man finds a back door into a military central computer in which reality is confused with game-playing, possibly starting World War III.
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 Defense Department'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.