• Women are facing threats and blackmail from a mob of anonymous strangers after their personal details, intimate photos and videos were shared on the social media platform Reddit.
• Underneath, men were posting vicious commentary about the women, including rape threats.
Women are facing threats and blackmail from a mob of anonymous strangers after their personal details, intimate photos and videos were shared on the social media platform Reddit.
The BBC has unmasked the man behind one of the groups, thanks to a second-hand cigarette lighter.
"£5 for her nudes, DM me."
"I've got some of her vids looking to trade."
"What are we gonna do to her?"
I felt sick as I scrolled through the images and comments online.
There were thousands of photographs. A seemingly endless stream of naked or partially dressed women. Underneath, men were posting vicious commentary about the women, including rape threats.
Much of what I saw was too explicit to share here.
A tip-off from a friend had brought me to these images. One of her pictures had been lifted from Instagram and posted on Reddit. It was not a nude but was still accompanied by sexual and degrading language.
She was concerned for herself and other women.
What I found was a marketplace. Hundreds of anonymous profiles were dedicated to sharing, trading and selling explicit images - and it all appeared to be without the permission of the women pictured.
It seemed like a new evolution of so-called revenge porn, where private sexual material is published online without consent, often by embittered ex-partners.
Not only were these intimate images being shared for an audience of thousands, but men - lurking behind the mask of anonymity - were teaming up to expose the real-life identities of these women, a practice known as doxing.
Addresses, phone numbers and social media handles were being swapped online - the women then being targeted with lurid sexual comments, threats and blackmail.
It felt like I had stumbled into a very dark corner of the internet, but this was all happening on a major social media platform.
Reddit brands itself as "the front page of the internet". It has built an audience of about 50 million daily users - roughly four million in the UK - by letting people set up and run forums, known as "subreddits", dedicated to all kinds of interests. Most subreddits are harmless, but Reddit has a history of hosting controversial sexual content.
In 2014, a huge cache of private images of celebrities was shared on the site, and four years later Reddit shut down a group which was using "deepfake" technology - a kind of artificial intelligence - to superimpose celebrities into porn videos.
Responding to these controversies, the US-based company introduced stricter rules and strengthened its ban on posting or threatening to post intimate or sexually explicit media of people without their consent.
I wanted to understand how women's intimate photographs were still being shared on Reddit and what it was like for those affected.
Then I wanted to find out who was behind it.
I could see that Reddit's ban wasn't working.
We found dozens of subreddits dedicated to sharing intimate images of women from all over the UK.
The first one I looked at was focused on South Asian women and had more than 20,000 users, most of whom seemed to be men from the same community, with comments in English, Hindi, Urdu and Punjabi. Some of the women I recognised because they had large social media followings. A few I even knew personally.
There were more than 15,000 images. We looked at a thousand of them and found sexually explicit pictures of 150 different women. All were being dehumanised as sexual objects in the comments. I was sure none of the women would have consented to appearing on this forum.
Some, like the one my friend discovered of herself, were images lifted from the women's social media and weren't explicit. But they were accompanied by degrading comments and sometimes requests to hack victims' phones and computers for nudes.
One woman we contacted says she now gets intrusive, sexual messages on social media "every day" after the group posted an image of her in a crop top from Instagram, alongside comments about raping her.
The men on the subreddit were also sharing and selling naked photos of the women. These images looked like selfies which had been sent between partners and were not meant for public consumption.
There were also videos - even more graphic - where it appeared as though the women had been secretly filmed during sex.
'I will find you'
One thread of messages featured images of a naked woman giving oral sex.
"Anyone got any vids of this [expletive]?" an anonymous user asked, using a derogatory name for her.
"I have her whole folder for £5, snap me," another said.
"What's her socials," asked a third.
Ayesha - not her real name - discovered videos of her were being shared on the subreddit last year. She believes she had been secretly filmed by an ex-partner.
She didn't just have to deal with the violation of her trust, she also faced a wave of harassment and threats on social media when her personal details were posted on the forum.
"If you don't have sex with me, I'll send it to your parents. I will come and find you… If you don't agree to having sex with me, I will rape you." Her harassers tried to blackmail her for more images as well.
"Being a Pakistani girl, it's not right in our community for us to even get sexual before marriage or anything like that - that's not acceptable," she says.
Ayesha stopped socialising or even leaving the house, and eventually tried to take her own life. After her suicide attempt, she had to tell her parents what had happened. Her mother and father both fell into depression, she says.
"I felt so ashamed of everything that was going on and that I'd put them in this situation," she says.
Ayesha contacted Reddit several times. On one occasion, a video was deleted almost immediately but it took four months to remove another. And it didn't end there. The deleted content had already been shared on other social media sites and eventually appeared back on the original subreddit a month later.
The subreddit that shamed and harassed Ayesha was set up and moderated by a user called Zippomad - a name that would eventually provide the clue to tracking him down.
As moderator, Zippomad was supposed to make sure his subreddit discussion group followed Reddit's rules. But he did the opposite.
Since first tracking his subreddit, I've seen him create new versions of it three times - after each previous version was shut down by Reddit due to complaints.
Each new incarnation used a variation of the same name, which includes a racial slur too offensive to repeat. Each one was filled with the same material - and each had thousands of active users.