Transcript for 'Sextortion' Becomes Growing Online Global Threat
It's been called a new tomorrow of sexual assault. Online extortion. What's driving this growing threat, tonight we hear from the victims, young, vulnerable, and exposed. Here's ABC's Lindsey Davis. Reporter: With the click of a mouse the beauty queen's moment to shine turned into her darkest days. I was happenway through my reign has miss California when I found out I had a stalker. Reporter: Class di wolf, 2013's miss teen usa said it was someone with an arsenal of private, personal images of her. I got an anonymous e-mail from someone and basically it was stating three things, if I didn't do what he said, he was doing to release all the photos that he had of them. Reporter: She was a victim of an online crime that is a growing concern. It's called sextortion. In wolf's case, she says she was shocked to learn the pictures even existed. I had no idea who he was talking about because I'd never taken photos before. Reporter: It pushes out a hacker took over the web cam on her computer and secretly recorded her for a year, watching her get ready for school in the morning and undress at night. He gave me three options. The first was to send him better quality photos. The second option was to snap chat him, and the third option was to Skype him for five minutes and do what he said. If I didn't, he would blackmail me. He did it. I would receive 30 e-mails a day of him harassing me, asking for me. Reporter: Her online manipulation lasted for several months until finally her cyber peeping Tom turned himself into the FBI and was sentenced to 1 months in prison, and the biggest surprise for wolf, it was someone she knew. The whole entire time I was receiving e-mails from this guy, I pictured a creepy guy in a basement halfway across the world, but then I found out it was someone I went to high school with that lived in my hometown. Reporter: But in many cases, the back mailer is anonymous. As students at George mason university discovered that this week. To hear there were two more cases was disturbing. Reporter: An e-mail from university officials sounded the alarm that unknown suspects gained the trust of two students over the internet enticing them to broadcast sexual acts over their web cams. Once they said, the suspects None of us in Jacksonville, violations for years, we've never seen anything like this before. Reporter: Chancellor entered online chat rooms popular with girls going by numerous online names. He posed as a teenage boy interested in skateboarding. He asked his prey to video chat and then strip and perform a series of specific poses all the while secretly recording them. One of the targets says she felt like his captor. As I'm doing this, he would be like no, this isn't right. do this right. You got to do it again. And that's where bag slave to him comes in, because I had to make sure I come plied. Reporter: He amassed more than 80,000 images and videos that he used to threaten the girls saying he would hurt them or their families if they didn't give him more. He labeled his files marking them done when he was satisfied with his blackmailing. Next to the victim's name he'd have notes to himself like I remember one was will try again. Another was a note on Facebook now. Samantha was 13 years old when she and a friend encounters him He was in a chat room when we were chatting with people we thought were our age. Asked us to flash our breasts, and he snapped a picture. Reporter: He resurfaced, ready to manipulate her. I was afraid and scared, and as a 13-year-old, you really -- you believe that someone is going to do those things they said they're going to do to you. Reporter: She says over the course of the next several hours chancellor directed her through his poses asking her to perform graphic sex acts she'd never heard of. Finally he seemed satisfied and left Samantha alone. She says she immediately deleted her social media accounts and never told anyone about the encounter. I was afraid every day he would come back and taunt me. Reporter: Chancellor told the FBI he sought out girls in their early teens specifically. He said because older girls wouldn't fall for his ploy. Reporter: He used multiple servers that hid his identity, routing his communications through other countries. That's how some of them get away with it according to an attorney. Local law enforcers don't know what to do. They don't want to prosecute or worry about offenders on the other side of the world which happens with these types of internet crimes. Reporter: Chancellor was prosecuted in 2014 and sentenced to 105 years in federal prison. Only about a third of his victims have been identified. They're encouraging more to come forward. Samantha says she's glad to see him put away. It was overwhelming but it felt good to confront the guy who caused me so much pain and suffering. Reporter: She said the experience has left her changed forever. I became suicide. I've attempted suicide. And I live with anxiety now. I can't walk down the street and feel comfortable if I get looked at by a strange man. Reporter: How concerned are you about sextortion. I think there couldn't be anything more important for our country to be focusing on as a new crime that needs to be really, really, really concentrated upon. What is sextortion. Reporter: The FBI put this video on their website counseling teens on how to protect themselves. Because they're not alone, Samantha says other girls shouldn't feel embarrassed if they fall for a scam. The best thing you can do is to reach out to someone who cares about you and you can trust and seek help. Reporter: For "Nightline," I'm Lindsey Davis in New York.
This transcript has been automatically generated and may not be 100% accurate.