Experts increasingly worried about 'sextortion' of minors online

computer hacker
Comstock Images | Getty Images

Sexual predators are enticing teenagers and even younger children to send lewd pictures of themselves, then blackmailing them to get more — a scheme known as sextortion that has authorities increasingly worried.

While it's too early to have firm statistics on sextortion, experts on child exploitation say the number of instances is unmistakably on the rise and has coincided with the explosive popularity of social media and the age of a camera on every phone.

"We're talking about kids with a lot of privacy and a lot of technology," said Michelle Collins, vice president of the exploited children division of the National Center for Missing and Exploited Children. "And they're at a sexually curious age."

(Read more: Endangered species?Why fewer teens are driving)

On Monday, federal authorities revealed that a five-week crackdown had led to the capture of 255 suspected child predators — among them two men believed to be sextortionists with dozens of victims between them. One is a former high school cheerleading coach.

Experts say sextortion usually starts when a child, typically a tween or early teenager, meets a stranger online, through social media or a chat site. The predator gains the child's trust and convinces him or her to send a lewd photo.

Then the predator uses that photo to blackmail for more, threatening to send the photo to the child's parents or friends — or publish it online for the world to see — unless the child provides something racier and racier.

In a case last month in Indianapolis, the FBI said a man pretended to be a young woman on Facebook, then made contact with teenage girls and offered to trade self-made photos.

And an Alabama man was sentenced in January to 35 years in prison for what was described as a massive sextortion scheme. To gain the trust of girls in at least six states, he posed as a new kid in town looking to make friends, or even as Justin Bieber, authorities said.

(Read more: Teen Drivers Nearly Double Car Insurance Premiums)

Once he had their trust, he turned friendly conservations into something more personal, talking them into sending a racy photo. That was all he needed to execute the blackmail and demand ever more revealing photos, authorities said.

"Predators take advantage of that misstep," said John Morton, director of U.S. Immigration and Customs Enforcement, which announced the crackdown Monday. "And teenagers make a lot of missteps."

Authorities say they are especially concerned because the technological nature of sextortion makes it easy for predators to victimize huge numbers of kids, and to do it around the world.

In one of the cases announced Monday, the immigration agency said a Puerto Rican man extorted as many as 80 children, including a girl thousands of miles away in California and one in the Netherlands.

And a confessed sextortionist from Indiana was sentenced two weeks ago to 40 years in prison after he admitted to tricking more than a dozen teenagers into performing lewd acts through a webcam.

The man, Richard Finkbiner, used a site called Omegle that offers random, anonymous one-on-one chats, prosecutors said. The teens thought they were looking at live video of the other person performing a sex act.

(Read more: Teen Angst:Retailers Fight for Relevance)

Instead, Finkbiner was showing them recordings, prosecutors said. When the teens performed sex acts on their own cameras, Finkbiner threatened to upload them to the Internet unless the teens made more recordings, prosecutors said.

The victims were 12 to 16 years old and lived in nine states.

Collins, of the National Center for Missing and Exploited Children, said the best weapon parents have to prevent their own children from falling prey to sextortionists is awareness — knowing it's easy for kids to get in over their heads online.

The center has a tip line for online threats, and most chat services offer buttons to report abuse. Collins said children need to know they must talk to an adult if they're uncomfortable, especially at a time when kids spend so much time wired.

"There is no online or offline anymore," she said.

By Erin McClam of NBC News