NEW YORK • When Kate's 13-year-old son took up Minecraft and Fortnite, she did not worry. He played in a room where she could keep an eye on him.

But about six weeks later, Kate saw something appalling pop up on the screen: a video of bestiality involving a young boy.

Horrified, she scrolled through her son's account on Discord, a platform where gamers can chat while playing. The conversations were filled with graphic language and imagery of sexual acts posted by others, she said.

Her son broke into tears when she questioned him last month.

"I think it's a huge weight off them for somebody to step in and say, 'Actually this is child abuse, and you're being abused, and you're a victim here,'" said Kate, who asked not to be identified by her full name to protect her family's privacy.

Sexual predators have found an easy access point into the lives of young people: They are meeting them online through multiplayer video games and chat apps, making virtual connections right in their victims' homes.

Criminals strike up a conversation and gradually build trust. Often they pose as children. Their goal, typically, is to dupe children into sharing sexually explicit photos and videos of themselves - which they use as blackmail for more imagery, much of it increasingly graphic and violent.

Reports of abuse are emerging with unprecedented frequency around America, with some perpetrators grooming hundreds and even thousands of victims, according to a review of prosecutions, court records, law enforcement reports and academic studies.

The New York Times reported earlier this year that the tech industry had made only tepid efforts to combat an explosion of child sexual abuse imagery on the Internet. The Times has also found that the troubled response extends to the online gaming and chat worlds.

There are tools to detect previously identified abuse content, but scanning for new images - like those extorted in real time from young gamers - is more difficult.

While a handful of products have detection systems in place, there is little incentive under the law to tackle the problem, as firms are largely not held responsible for illegal content posted on their websites.

Six years ago, a little more than 50 reports of the crimes, commonly known as "sextortion", were referred to the federally designated clearing house in suburban Washington that tracks online child sexual abuse.

Last year, the centre received more than 1,500. And the authorities believe the vast majority of sextortion cases are never reported.

There has been some success in catching perpetrators.

In May, a California man was sentenced to 14 years in jail for coercing an 11-year-old girl "into producing child pornography" after meeting her through online game Clash Of Clans.

An Illinois man received a 15-year sentence in 2017 after threatening to rape two boys in Massachusetts - adding that he would kill one of them - whom he had met over Xbox Live.

"The first threat is, 'If you don't do it, I'm going to post on social media and, by the way, I've got a list of your family members, and I'm going to send it all to them,'" said Mr Matt Wright, a special agent with the Department of Homeland Security. "If they don't send another picture, they'll say: 'Here's your address - I know where you live. I'm going to come kill your family.'"

It makes sense that the gaming world is where many predators would go. Almost every teenage boy in America - 97 per cent - plays video games, while about 83 per cent of girls do, according to the Pew Research Centre.

There are many ways for gamers to meet online. They can use built-in chat features on consoles like Xbox and services like Steam or connect on sites like Discord and Twitch.

The games have become extremely social, and developing relationships with strangers on them is normal. "These virtual spaces are essentially hunting grounds," said Dr Mary Anne Franks, a professor at the University of Miami School of Law and president of the Cyber Civil Rights Initiative, a non-profit group dedicated to combating online abuse.

This autumn, the Federal Bureau of Investigation rolled out an awareness campaign in middle and high schools to encourage children to seek help when caught in an exploitative sexual situation.

New Jersey police departments were flooded with phone calls from parents and teachers alarmed about paedophiles lurking on game sites and in chat rooms. So law enforcement officials from across the state took over a building near the Jersey Shore last year and started chatting under assumed identities as children. In less than a week, they arrested 24 people.

The authorities did it again, this time in Bergen County, a suburb close to New York City. They made 17 arrests.

And they did it once more, in Somerset County, arresting 19. One defendant was sentenced to prison, while the other cases are still being prosecuted.

After the sting, officials hoped to uncover a pattern that could help in future investigations. But they found none; those arrested came from all walks of life.

When announcing the arrests, the authorities highlighted Fortnite, Minecraft and Roblox as platforms where offenders began conversations before moving to chat apps.

NYTIMES