The 1992 movie Sneakers is the closest Hollywood has gotten to accurately portraying information technology in general, and computer security issues in particular. It was directed by Phil Alden Robinson, who also did the 1989 Field of Dreams. Starrynight also informs me that Branford Marsalis, the great sax player and brother to Wynton Marsalis, did a lot of work on the soundtrack.
The good guys are a "tiger team" of experts, who make a living by analyzing the security procedures, hardware and software of their clients in order to improve security. The introduction sequence shows them pulling off a combination of social engineering, surveillance, and good old-fashioned breaking & entering to withdraw a large sum of money from a bank.
Their leader is Martin Bishop (played by Robert Redford), an aging hacker whose leadership skills are more useful than his computer skills. The team of misfits includes Donald Crease (Sydney Poitier), an ex-CIA agent who's left government service for reasons unknown, Whistler (David Strathairn), a blind electronics genius, Mother (Dan Akroyd), the resident conspiracy-theory-spouting paranoid, and Carl (River Phoenix), the kid who gets stuck with the jobs the others can't or won't do (he seems to spend all his time in the ducting). They are joined by Liz (Mary McDonnell), Marty's ex-girlfriend.
The plot revolves around a decryption chip, one that supposedly can break into any American-made encryption system. Marty's past gets them involved in a wild chase involving Russian diplomats, fake NSA agents, a megalomanic villain (Cosmo, played by Ben Kingsley), and a murder or two. It takes all the team's skills, equipment, and a bit of luck to stay one step ahead of the various powers-that-be that want the chip, and when it is stolen, it is up to them to keep it out of the wrong hands.
What makes this movie so great is the spot-on portrayal of social engineering and other cracking techniques (no mysterious "virus" that magically eats up the enemy database), the surprising dearth of plot holes (or even scientific/technical holes), the mature, non-hysterical handling of issues (the main plot is chillingly prophetic, years before the Clipper chip came onto the scene), the humor (lots of inside jokes) and the extremely quotable lines. Of course, the top-caliber actors don't hurt a bit.
Even though I think the "no more secrets" ending is a bit of a strain on the credibility, it's still far better than Hackers, The Net, and all those other script-kiddie inspired movies out there. Its action sequences even give Mission Impossible, Enemy of the State, and others a run for their money.
Marty: Give him head?
Whistler: Be a beacon?
Most details from www.imdb.com and various HBO trailers and interviews.