Amanda* recalls the shock of seeing her face among so many underage girls – some of them from her school in northern NSW. "It was terrifying," she says. "Just to know that someone is out there looking for naked photos of me and doesn't care how I feel is very intimidating."

More than 2000 photos of students from at least 70 Australian schools were reportedly uploaded on the online chat forum, which was taken down on Friday by police. Some of the images exposed young girls engaged in sexual acts. The majority were nude selfies taken in the privacy of their bathrooms or bedrooms and shared by former partners, without the girls' consent.

Amanda's photo in a low-cut red top and make-up was stolen from her Facebook page and posted on the online chat forum one Tuesday morning in June, by someone scouring social media for something more explicit of her. Finding and sharing such private images was dubbed a "win" by the site's users, who offered "bounties" – promises to release caches of pornographic pictures – to encourage young hunters.

The full names and faces of hundreds of teenagers appeared on the wanted lists for nude images, with directives to "Go get her boys!"

Amanda, now 16, says there aren't any explicit images of her to find – she doesn't post them because of the risk they might be shared and harm her future career prospects. But most of the schoolgirls exposed on the "Aussie sluts" site were not so fortunate. "It would be absolutely gutting and a horrible feeling to know that these people have this of you and that it can be held against you for the rest of your life," she says.

"I guess the scariest part of it is that I don't know who put my photo up there – it was probably a guy who had access to my Facebook and has access to me in real life, someone who goes to my school, someone I trust. I am insanely creeped out by the idea that they would go that far to see me naked."

She didn't ask for her image to be removed for fear the virtual abuse might evolve into real-life stalking or harassment. A young woman who did complain about the use of her naked image on the site was told it was her fault for behaving like a "slut". "When women are this loose with their sexuality and lifestyle choices, this is just the fallout," one user claimed.

'The worrying thing is that you can't control it'

"Where's the moral compass gone for those young people posting these pictures?" asks Katie Acheson, chief executive of Youth Action, the peak body for young people and youth services in NSW. "Why do they think it's OK?"

Such questions might be broken into two, in turn: Why do young people share naked images of themselves? And why do some people exploit and abuse those images so keenly?

Some users of the school porn site bragged about showing photos sent to them personally. Others issued orders for images of girls from specific schools or suburbs. "Who has nudes of this bitch? I hear she throws it around!" was one comment. But the problem goes beyond a single online chat forum. Two senior students at Brighton Grammar, in Melbourne, were recently expelled for setting up an Instagram account to "slut shame" girls as young as 11, while a student at nearby St Michael's Grammar School reportedly created a Dropbox folder for sharing explicit images of teens.

Acheson says uploading explicit selfies is an expression of healthy sexual development for many teenagers. It's the modern equivalent of taking nude Polaroids or filming sex tapes for the VCR.

But there's a disconnect between making such images and understanding the risks at play, she says. "The act of sharing is something young people have always done. It is an obvious continuation of the fact that young people are very much living in the virtual world as part of their everyday," she says. "The worrying thing is that you can't control it. The ramifications are much greater than writing someone's name on the toilet door at your school. It's around the entire world and that is much more scary."

David Vaile, co-convenor of the Cyberspace Law and Policy Community at the University of NSW, says a culture of reckless sharing of information has been fostered by sites such as Facebook and online bulletin board 4Chan. "The idea is 'Don't think too much, don't have any respect for your own information or security and don't value anybody else's'," he says.

"Nobody wants to think twice and realise they may be hurting someone. You get this toxic environment of stalking and harassment, and people become desensitised to the reality of the person at the other end of the camera. There's this competitive bragging and trading circle. The younger you are, the harder it is to join the dots and project the consequences."

High school student Lily*, 17, from Lismore, in north-east NSW, says posting explicit photos or sex videos online is "pretty normal" behaviour among her peers. "I get asked for nudes all the time and give them out. It's how people connect these days," she says. "The girls take them to show to their boyfriends or to have some fun. Guys love to take pics of their dick.

"It's how people show off what they've got to offer, like advertising. I know girls who will deliberately have sex in public places with boyfriends and then talk about it in the playground with their friends – no one talks about it as a bad thing."

A two-year study of sexting among young people, published by the Australian Institute of Criminology last November, found 49 per cent of teenagers have sent a sexual picture or video of themselves to someone, while more than two-thirds have received such images. The teens surveyed gave several reasons for sending explicit images, including: to be "fun and flirty", "as a sexy present", to "feel sexy and confident" and "because I received one".

Most sexting is done consensually and with only a few partners, the study found. But the researchers highlighted the gender double standards at play, with boys less likely to be shamed or humiliated by the circulation of such images.

Amanda says nude photos of girlfriends have been shared openly in her school playground – either as an act of revenge by ex-partners or to laugh about their "scores" with friends. "The girls get really harsh comments about their body and end up really scared about being intimate with people," she says. "If someone is proud of their body and of a legal age to share it with a romantic partner, that's fine. But when it goes to people who are not the target audience, then it becomes malicious and attacking."

Some people she's met on Facebook have pressured her to send nude selfies. She says such conversations usually start with a request to "send me something sexy" or "something with a little chest in it", before demands for something more explicit. "It's the same sort of pressure that makes girls start to dress in tighter clothing or to be more sexual," she says.

"I think there's a lot of violence in it, whether it's intended as having power over women or whether it's just a 'bro' mentality some guys have. It's a culture where nudes are seen as something to be sold or traded. It's just disgusting to think these people don't see girls as anything more than what they show in their photos."

Telling girls not to take such photos in the first place is blaming them for such behaviour, says Professor Catharine Lumby, a social media and gender expert at Macquarie University. "Young women should be free to explore their sexuality with consent, without being told they are bad people, let alone being publicly shamed for that," she says.

"We need to put a lot more focus on the ethical responsibility of the young men doing it. A minority of young men have the attitude that any girl who shows her breasts or takes her kit off is up for it, not only to have her image shared but for misogynistic comments. The guys who do that are operating out of a combination of fear and desire – they desire attractive young women and at the same time they are terrified of them, and that makes them angry, and they show that by sharing these photos."

Acheson says young people need to be taught how to share images safely online – like a contemporary form of sex education. "It comes back to teaching young men and women to value themselves and others. The first part is teaching them that if you are going to send a picture, you need to have a conversation about where it is going and who is allowed to share it," she says.

"It's about teaching young people how to keep themselves safe. Essentially, what we need is a condom for the iPhone."

*Names have been changed