I am looking for an American movie in which a hacker is forced to access US Police information by his twelve year old son's kidnappers.
The Movie Swordfish fits this description, albeit with a few discrepancies:
Earlier on in the film, however, Stanley is forced to infiltrate a government system.
From IMDB plot synopsis:
That scene was a pretty unique part of the movie, if it included that its definitely Swordfish.