Jennifer Lawrence is among actresses whose naked photographs were posted on the website last week

According to denizens of the darker corners of the internet, where criminality and vice thrive on private forums, the pictures had been around for months.

A small group of hackers, linked by their obsessive interest in finding explicit images of female celebrities, would email each other stolen photos and videos they had obtained.

They would compete for ‘wins’ and see who could get the biggest ‘score’ — depending on the degree of a victim’s fame. To these internet perverts, women were just objects and trophies.

It isn’t clear what these men ultimately intended to do with their haul of celebrity porn — amounting possibly to thousands of images of more than 100 actresses, performers and even Olympic athletes. But making money was clearly a possibility and so was blackmail.

So far, though, these cyber-thieves have not got much more than a couple of hundred dollars for their sordid activities, and now have the FBI on their tail into the bargain, after one of their number broke rank and started leaking them on to a controversial picture-sharing website last Sunday.

Over the past week, it has emerged that at least 400 pictures have been posted online.

As for the women stars, they were naturally shocked and humiliated as their Hollywood PRs rushed to condemn the publication of the most intimate contents of their clients’ digital photo albums.

The photos and videos were, it is believed, stolen from iCloud — the global system that stores photos and videos recorded on iPhones and other Apple devices.

The victims include the Oscar-winning young actress Jennifer Lawrence, ex-Downton Abbey star Jessica Brown Findlay, Spiderman heroine Kirsten Dunst, busty supermodel Kate Upton and reality TV phenomenon Kim Kardashian.

A list of celebrity names published anonymously online mentions scores more targets including actresses Kate Bosworth and Selena Gomez, singer Rihanna, British models Cara Delevingne and Kelly Brook, and TV presenter Cat Deeley. Some are shown naked, others topless and a few are sexually ‘in flagrante delicto’.

One video — reportedly showing Brown Findlay, who played Downton’s Lady Sybil, engaged in somewhat unladylike behaviour — was watched more than a million times online within hours of being posted.

Celebrities who are used to controlling their public image with a vice-like grip have had to watch helplessly as millions around the world have been able to access their most private moments.

So-called Celebgate began last weekend when someone calling himself ‘OriginalGuy’ posted explicit pictures of Jennifer Lawrence and other stars on a notoriously sordid but influential internet ‘image board’ called 4chan that attracts 12 million visitors a month.

The site is used principally by young men, and its guarantee of anonymity (users don’t have to register before posting messages) has seen it described as ‘the ninth circle of Hell’.

And yet it was set up by a sweet-faced 15-year-old schoolboy, Christopher Poole, in his New York bedroom in 2003. He wanted to offer a forum for people to put whatever they wanted online with no rules and no fear of prosecution.

His business backers in a newer internet venture include some of the founding investors of Google and the news site Huffington Post.

In 2009, Poole was voted the world’s most influential person by Time magazine although 4chan users reportedly rigged the poll.

His vision of a completely free, unrestricted exchange of information is, after all, what the British computer scientist Sir Tim Berners-Lee envisaged when he invented the World Wide Web.

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Downton Abbey starlet Jessica Brown Findlay (left) and actress Kirsten Dunst (right) were also targeted by hackers

But be careful what you wish for.

The original aim for 4chan — as a slightly risque forum for teenagers — soon turned into an internet cesspool as users exploited it to spread the most vile material.

In so-called ‘shock posts’, they try to outdo each other in offensiveness. For example, pictures of dead people and car accidents are popular, as is extreme pornography and virulent racism.

Despite being the only type of material that is meant to be banned from the site, child porn is regularly posted. ‘Pranks’ have included taunting the family of a suicide victim, starting bomb and school shooting scares, encouraging young fans of the singer Justin Bieber to harm themselves and triggering a false rumour that Apple founder Steve Jobs had died of a heart attack.

Anyone who offends the 4chan community or other cheerleaders for the out-of-control internet can expect revenge attacks. Ater the credit card companies Visa and Mastercard stopped handling donations to the whistle-blowing site WikiLeaks, they were targeted by on-line vigilantes who managed to crash their websites.

Indeed, many members of the sinister mask-wearing international vigilante hacking group Anonymous started out as 4chan members.

Most of 4chan’s most offensive content is posted on its digital message board, called /b/, where members call themselves ‘/b/tards’ and live up to the title with displays of vicious misogyny.

Countless pages are devoted to ‘revenge porn’ — once the unpleasant practice of posting publicly compromising photos of an ex-lover, this is now a catch-all term for any compromising photos of women published online without their consent.

An even more revolting trend is for so-called ‘creepshots’, in which men try to photograph the bodies of women or girls — often under-age — whom they have seen out in public.

Once again, marks are awarded for the most compromising shots. If challenged over why they are allowing pictures that have been taken up a teenager’s skirt, websites like 4chan say it was legal as it occurred in a public place.

Revealing photographs of model Kate Upton (left) and reality star Kim Kardashian (right) are also believed to have been obtained by hackers

Most sickeningly, some 4chan users felt the site wasn’t sufficiently pornographic and formed a break-away message board, AnonIB, where hackers calling themselves ‘iCloud rippers’ advertise their services to break into the online account of any woman and download her private photos.

The site’s so-called ‘obtained pictures’ section lists the email and iCloud addresses of dozens of women. When a hacker successfully breaks into their account, they notch up ‘win’ and post any embarrassing pictures they find.

Experts believe this latest celebrity stalking began in what is known as the Dark Web (or Deep Web or Underweb) a noxious matrix of encrypted websites that allows users to surf beneath the everyday internet with complete anonymity.

It has existed for more than a decade and has been used by criminals to deal in drugs, sell weapons and view horrific child pornography. Much of the trade is done with bitcoins, the controversial digital currency which is increasingly used by cyber-criminals to cloak their activities.

Users of 4chan’s /b/ messageboard reacted with predictable glee when the leaker of the naked celebrity snaps chose their forum to announce their existence.

OriginalGuy, as he calls himself, sought donations in bitcoins from anyone accessing the images. The photos, he said, had been ‘privately traded’ in this currency after being stolen from celebrities’ accounts on iCloud.

Subsequently, more pictures appeared on mainstream picture-sharing websites where they were labelled ‘The Fappening’. (‘Fap’ is slang for masturbation.) OriginalGuy has said his group also has an explicit video of Jennifer Lawrence that they are willing to sell.

Hackers compete to get the most famous victim

Lawrence and several other victims have admitted the photos are genuine and have threatened to prosecute anyone identified as having posted pictures of them.

But internet experts warn that it may be impossible to remove the images from the web permanently.

Six days on from the original leak, the identity of the hacker — or it is widely assumed, hackers — remains unclear.

In theory, every hacker leaves a ‘digital trail’ and it has been reported that some of them may be as far afield as Holland and the U.S. Mid West.

After Apple insisted there had been no widespread breach of its iCloud — if true, a huge relief for the millions of ordinary people who store their photos and other private files on it — it has been suggested that the thieves simply used various trial-and-error techniques to find out specific celebrity email addresses and passwords.

Meanwhile, the release of more embarrassing photos and videos is expected. Also, it has emerged that some of the already published photos — of 18-year-old U.S. gymnast McKayla Maroney and an MTV actress named Liz Lee — were taken while they were under-age.

Cynical users of the website 4chan went on Twitter to encourage girls to post pictures of themselves naked — supposedly to show ‘solidarity’ with Jennifer Lawrence.

Reddit, a hugely popular but sleaze-filled internet forum largely owned by Conde Nast, publishers of Vogue and GQ, has been enthusiastically spreading the offending pictures.

Sensing a backlash that might damage the parent company’s reputation, its editors urged members to donate to the Prostate Cancer Foundation ‘in honour of Jennifer Lawrence’. But the charity — as soon as it discovered the donations — returned the money, stating publicly that it was considered tainted.

Predictably, such an ethical stance did not impress Reddit users, who complained about the charity’s reaction.