Secrets of the stars are being spilled as campaigners threaten studios' control over product and people.
Miley Cyrus and Gerard Butler had personal details put online by the anonymous Hollywood Leaks hacker group.
Behind the feelgood story lines and happy endings of even the most bland Hollywood movies lurks a formidable publicity machine that exerts a grip on every aspect of a film's life.
From keeping scripts secret to vetting press interviews with stars, setting embargoes and filming on closed sets, big Hollywood studios jealously guard their projects.
Hundreds of millions of dollars are often at stake. One slip-up can kill a movie - and a dead movie usually takes a few careers with it.
So it is with growing horror that the movie business and its galaxy of celebrities have witnessed the emergence of a group of computer "hacktivists" dedicated to cracking open Hollywood's most valuable secrets and releasing them for all the world to see.
Calling themselves Hollywood Leaks, the anonymous hackers have stolen scripts for coming movies, revealed nude photos of celebrities and placed their personal phone numbers and email contacts on the internet for all the world to see.
Victims have included action star Gerard Butler, whose email address was put online, and singer and actress Miley Cyrus, whose personal details were also hacked.
The script of the upcoming Tom Cruise movie Rock of Ages, also starring Malin Akerman and Julianne Hough, was leaked, as were scripts for the forthcoming Footloose remake and the crime drama Gangster Squad, with a roster of big names including Sean Penn and Ryan Gosling.
Hollywood Leaks came from the underground world of computer hacking that has already produced groups such as Anonymous and LulzSec, whose targets have ranged from the CIA and the US Senate to PayPal and Bank of America.
Hollywood Leaks wants to destroy the carefully constructed Hollywood information system that has grown up since the movie business exploded into popular culture in the 1920s.
Using gaping holes in the major studios' computer network security, Hollywood Leaks is on a mission to upset an entire industry's way of doing business.
"Once they get into someone's network they can do a lot of damage," said Mark Russinovich, a cyber security expert and technical fellow at software giant Microsoft.
Hollywood studios often force journalists and reviewers to sign non-disclosure agreements when they get previews of upcoming movies. They ban certain questions and declare personal lives off-limits.
And when they do want to hint at a movie's content - such as with a big special effects feature like James Cameron's Avatar - it is by tightly controlled releases of photographs or clips that they themselves control.
Gayl Murphy, a Los Angeles celebrity interviewer, said: "These guys are very serious about what they do."
They have been from the beginning. As the studio system emerged in the 1920s, a new breed of film executives discovered huge monetary potential in their films, stars and even composers and costume designers.
Stars promoted products because they were told to, appeared in magazines next to copy written by studio PRs and even dated other stars as instructed.
"Studios controlled everything and everyone, as best as any corporation could control individuals. Contracts ruled everything and if you were under contract to a studio you were, in essence, owned by them and you did what you were told to do," said Professor Marsha Orgeron, a film history expert at North Carolina State University.
Though the power of the studios waned as the contract system broke down, the basic philosophy of strict message control has remained.
Big-budget movies became huge money-making machines, often with secretive commercial tie-ins, and with a strictly controlled PR message.
"The difference between Hollywood and other industries has to do with the monetary stakes, which are extraordinary, and the nature of the product," said Orgeron. Hollywood Leaks now threatens the mystique and mythology at the heart of the movie business and so also jeopardises its huge profits.
Of course, the dirty secret of Hollywood studios and the most powerful PR agencies is that they often love a good leak.
Stars rail against the paparazzi, but many publicity agents - and some of their more desperate clients - will happily tip off a photographer.
"There is no activity that Hollywood marketing executives will not do," said Richard Laermer, a celebrity expert and PR consultant.
But what is terrifying for movie executives, PR agents, celebrities and studio heads is the lack of control that Hollywood Leaks is bringing into the process. Injecting an anarchic hacker philosophy into one of the most carefully managed industries in the world is a nightmare come true.
"That is going to drive the studios insane," said Murphy.
Which, for Hollywood Leaks, is the point. The unknown hackers behind the group have sprung from a hacktivist culture that celebrates the concept of "lulz", which is tech slang for amoral mischief and creating havoc outside societal boundaries.
On the group's Twitter feed, updates urge followers to call the celebrity phone numbers released.
"People can't take a damn joke. We do it for the lulz," reads one tweet.
RUNNING THE SHOW
During the golden age of Hollywood, the "studio system" emerged whereby nearly all popular films in America were made by a handful of studios on their own lots, with staff under long-term contracts.
This gave studios immense control over their projects and the lives of their top actors.
The studio system broke up under pressure from a federal anti-trust lawsuit and the decision by billionaire Howard Hughes, who part-owned the RKO studio, to break up his business.
Actress Lucille Ball quipped: "I regret the passing of the studio system. I was very appreciative of it because I had no talent."
The modern world of Hollywood guards its future movie projects and its stars' reputations every bit as forcefully. Stars and studios employ legions of PR executives and masters of spin.