Transcript for Inside the fight to take down online prostitution review boards

We're about to go inside an undercover infiltration, police infiltrating and arresting a group of men, including some high-power tech executives, for arranging prostitutes on internet message boards. Many women are trapped in a world of sex trafficking by debt and fear. Tonight we explore the struggle to protect them from exploitation by holding the buyers accountable. Here's my "Nightline" coanchor juju Chang. Reporter: It may seem like an ordinary guy easy out, complete with nachos and beer. But this is an undercover operation. A Seattle police officer infiltrating an exclusive group that calls themselves the league of extraordinary gentlemen. Police say their common interest, Korean prostitutes. Also known as k-girls. You're about to witness an unprecedented prostitution sting. Everybody put your hands on top of your head. Put your hands on top of your head, do it now. Reporter: One that uncovered a secret network of online review boards. Websites for rating and recommending local prostitutes. What district attorney Val Ritchie calls -- Yelp for prostitution. She was taller than the 5'3" advertised, really 5'7", 120 pounds. Wonderful, natural C cups and full hips -- Reporter: Website users caught in the drag net, tech executives and white collar professionals from an Amazon software develop tore a high-level Microsoft director. We calculated they were spending $30,000 to $50,000 a year on this. It's a simple to use website. You can look at the girl. Okay, that girl looks interesting. You can go to her reviews, see if she is providing the services that you want. Tattoos, piercings, no scars, moles. Reporter: Prostitution review websites are a prolific corner of the illicit online sex trade. Tna review, the erollic review, cover just about every city in America, complete with customer reviews and often escort ads. But not all of these online communities ever end up meeting in real life. What surprised you most about the guys that you were meeting up with? I guess the fact that they were just -- they were like the people living next door. Reporter: The undercover detective who infiltrated this group has asked us not to show his full face. Everybody would order drinks, eat food, talk about, you know -- the latest prostitute that they've had sex with and you know, trends going on. Reporter: Parts of these conversations so sexually graphic, we can't air them. There were waitresses that were -- seemed a little offended. Reporter: The police investigation resulted in the shutdown of three websites. The review board and its two korean-focused offshoots, the league and k-girl delights, as well as controversial charges for some of the men caught in the dragnet. We have charged the people who were putting the content on the website with a felony charge of promoting prostitution. And so in what way does that promote prostitution? In what way is that pimping? The men post reviews and share information. So it goes beyond just a review. And then on to a recommendation. You have to go see this person, she's amazing, go see her before she leaves. Creating demand? Exactly. Reporter: Felony pimping charges for posting reviews on a website has never been attempted before in the U.S. For valiant Ritchie -- valiant is his real name -- it's a focus on demand, not supply. Our understanding of people in prostitution based on years of experience is that most people in prostitution are exploited. And so criminalizing them doesn't work from a criminal justice perspective. At the same time we understand that the exploitation that is driven through sex buying is caused by the buyer. The buyer needs to be held be theable. Reporter: There are many who strongly disagree, including unsurprisingly the men involved in the sites. But all declined to speak with us on camera. The argument though being you sacrifice these men's lives in order to further your career, to get the headlines, to get the national attention. The main focus for us is on dismantling these networks of buyers who are creating this vociferous demand for exploited women. Reporter: We've come to Bellevue, Seattle's wealthiest suburb. Hermes, Prada. To learn more about the Korean prostitution ring here and why some say this case could change the way sex buyers are prosecuted across the country. The idea broth they wills were being operated out of this upscale, suburban apartment building, lots of fancy people in the area who have no idea that sex is being sold right next door. There were several Korean brothels raided in this case. The 12 women found inside release the without charges. Described by police as trafficked. We tried to track them down but they seem to have scattered to the wind. It is really hard to get a genuine glimpse inside one of these Korean brothels. No one will talk to you, no one will admit to anything, because there's too much fear. Tiers too much shame. There's too much criminality. We went to a guy who ran one of these brothels. He actually agreed to talk to us. Michael durnel managed -- He's opening the door, hi. Reporter: -- Two of the Bellevue broth they willed. When they were busted he served 45 days in prison. How do you go from a guy with a wife and a kid to suddenly running a brothel? I was a client. To me it was that excuse, you know. I'm paying for it, it's not cheating. Reporter: Durnel says he fell in love with a Korean prostitute who told him she was in debt back home. So he says he decided to help her. He left his family and job and they opened up a brothel together. The one to the right? Yes. The big gleaming skyscraper, that's the brothel? That's one of them, yeah. You were booking clients to sleep with prostitutes? Correct. That fits the definition of a pimp, doesn't it? I guess it does. My understanding is that you heard a lot of stories that you say broke your heart. There's a lot of different stories on why people come over and do that, that job. Some of them just want to start a business. Some of them, their families will get hurt or death. One girl, I asked her why she doesn't just run, and she says she tried. And they find them. Reporter: Durnel repeatedly told us he deeply regrets his choices, because he saw firsthand the damage it did. You feel like the piece of the soul for the girl is gone. Reporter: While he says he was never personally involved with the review board or any site, he says many of his clients were avid users. I would ask my clients if you liked her, review her. Reporter: When it comes to the police sting that took down those sites and his brothels with it, durnel has his criticisms. They said they rescued all these women. They said that people were holding them captive. This came out of law enforcement's mouth. Who did they save? Every girl they let go, every girl's back in the business. They just go someplace else. You think these women are doing it voluntarily? Well -- it depends on what you're looking at as voluntarily. I mean, they're moving on their own. Nobody's holding their passports. Yet isn't the fear and the debt that you just described to me holding them cap sniff. Correct, yes. But again, it's not all these girls are being held like that either. How do you know which ones are and aren't? You don't. Reporter: Brad miles of the anti-trafficking group polaris says debt bondage is a common factor in the Korean networks. Debt bondage is different from debt. It's a particular type of predatory, manipulative debt where fees and interest rates and other hidden costs and all these other things kick into gear so that the person, the debt grows faster than the person can pay it off. Then you have these customers who think that the women are there voluntarily but the customers don't understand the full picture. Reporter: We did meet with seattle-based sex worker who's speaking out in support of the review sites. The work room is in the back. This is where you see clients? This is where I see clients. Usually the light is more like -- this. Reporter: Magny Mcneil, a popular sex work blogger, says the sites provide a valuable safety tool. Why does it make it safer to book somebody online? People are afraid to sell their pianos online, why would selling sex be safe? Because of reputation. Ebay, if somebody's got 98% positive reviews on Ebay as a buyer or seller, that lets you have confidence in dealing with that person. Reporter: Alisa Bernard, who calls herself a prostitution survivor turned activist, says she knows firsthand review boards don't make things any safer. I had been raped multiple times. Held against my will at least once. I was strangled. These were all by review board guys. You know. Again, your line keeps getting pushed further and further and further to get those good reviews. Because you're afraid of a bad review? A negative review could get you kicked off the board. Reporter: While the debate continues, prosecutor Val Ritchie is showing no signs of stop. In fact, nearly a dozen more men have been arraigned as part of the review board investigation. Ritchie's mission, to end sex buying altogether. This is the oldest profession. How can you possibly hope to eliminate it? I would argue that it's the oldest oppression. And that the one way we can try to eliminate it is by helping men realize that this isn't serving them either. Reporter: Ritchie travels across the U.S., telling other states' attorneys about demand-based prosecution. His hope, that they too will take on similar cases. It would be a great step forward in reducing nationwide exploitation if those review boards did not exist. Reporter: For "Nightline," I'm juju Chang in Bellevue, Washington. Our thanks to Ju Ju for that report.

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