You know that like button on facebook? You might wish there was a don't like button for the pempb who pulled this scam. It went on for years and involved thousands of people, none of whom knew they... See More
You know that like button on facebook? You might wish there was a don't like button for the pempb who pulled this scam. It went on for years and involved thousands of people, none of whom knew they were caught up in one of the biggest fakes ever on facebook. Ah, the internet, playground for every pajama-clad pretender looking to pull a fast one, for profit, attention, or perhaps just the twisted satisfaction of messing with someone's head. They are complete psychopaths. I could be chatting with a guy. Reporter: Case in point/ -- nev shulman's head. A new york photographer, nev fell for a gorgeous 20-something in michigan only to discover that, oops, she was actually a middle-aged mom. The whole cyber-saga caught on tape by his brother and a friend and turned into the indie blockbuster "catfish." Why were you so captivated by her? Why this anonymous person on the internet? It was different. It was something new. It was a little mysterious. Reporter: The hit film became a hit tv show on mtv. Nev now playing dr. Phil to other lonely hearts who've been duped, like this blonde who learns that the male model she's been cyber-dating is, surprise, another woman. I mean, who does that? That is just so . Reporter: Multiply that stunned reaction by 1,000 and you will begin to understand internet hoax so vast and elaborate it makes what happened to nev look like an e-mail typo. It started with a pitch-perfect combo of pictures and posts that just hooks your heart -- a young boy fighting a brave battle with cancer. His name -- eli dirr, or warrior eli. Taryn wright, from chicago, stumbled across the story through a friend. I think he had three different types of cancer at one point. Reporter: And how old was he? He was about to turn 6. Reporter: That's a lot of cancer. It was a lot of cancer. Reporter: The internet had been humming with his story for years, cancer support pages on sites like alex's lemonade stand. The storybook family hailed from saskatchewan, canada. Eli's dad? A handsome mountie, of course. His mom, dana? A pregnant trauma surgeon with n. Right. It just seemed, like, really easy to, like, fall in love with them. Reporter: This 18-year-old in california, who asked that we not reveal her identity, became a faithful supporter of eli's. Like so many others, she devoutly wore eli's bracelets and ribbons sent in care packages from the family. I would spend my lunch breaks at high school passing them out to all my friends and saying, "wear this to raise awareness to childhood cancer." Reporter: Then, out of the blue, a heartbreaking mother's day post that would send eli's dedicated followers into mourning. J.S. Dirr solemnly writes that his wife had been hit by a drunk driver. She survived just long enough to give birth to a baby girl. The web erupts in sorrow, hundreds of people posting their condolences. But nev shulman says such a surplus of tragedy should have sent up red flags. If the person you're talkg to has a series of family incidents, illness, oftentimes cancer, which we see a lot -- Reporter: Miraculous survival. Car accidents. Yeah, things like this, something to, to watch out. Reporter: Taryn wright reads the story and desperately tries to get more information. Oddly she can't. I googled the name of the person that had died. And there were no news google hits. And just the news value of a mother of 11 children dying on american's day -- Reporter: It should have been covered. Exactly. Reporter: So at that point, are your alarm bells ringing loud? Yes. At that point, they were super loud. Reporter:N A HUNCH, SHE Tries searching the web for other places the dirr photos might have appeared. Lo and behold, this image of eli's siblings in sunglasses posted on j.S.' Facebook page also appears on the site of a popular mommy blogger in, of all places, south africa. So you contacted her and said what? I said, "hi, I'm taryn wright from chicago." There was an e-mail saying, "i think that your pictures of your children are being used by somebody." And as I clicked more and more, I just saw more and more photos. Reporter: Photos of tertia albertyn's kids adam and kate identified as the dirr children jude and lily. And not just once -- I probably discovered over 70 images of my children. Reporter: But it wasn't just tertia's photos that were lifted. The entire dirr family, the birthdays, the memories, all of it was a fiction stitched together with purloined photos from various unsuspecting uploaders. Pregnant dana? She's actually a photographer from new york. The sweet and brave little eli? Those photos belong to jenny. Her son adam is a healthy kindergartner who has, thankfully, never had cancer. And eli's dad, the dashing mountie j.S.? I had, it's elizabeth vargas. Come up. Thank you. Well, we found him, not on horseback on the canadian tundra, but in an apartment in new york city, just a few blocks from our abc news. His real name is ryan. And it turns out he has very little in common with his alter ego, j.S. So just to be clear, you're not a canadian mounty? Am not. And you don't have 11 children? I don't have 11 children. Reporter: Back in chicago, taryn wright has unraveled a decade-long deception, but it's the victims who will hand over the most crucial clue. Remember those rubber bracelets and the care packages? Well, the return address wasn't from canada where the dirrs said they lived. It was from ohio. Because of his top secret mounty job, he apparently had a sister in the united states that would send out this for the family. Reporter: How convenient. Right. Reporter: And who was the sister in the united states? The sister's name was emily dirr. Reporter: But unlike the fake family she created, emily dirr is real. That's the mistress of deception right here in a sweatshirt, munching on a snack, outside her parent's house in ohio. Emily dirr declined our invitation for an interview through her attorney. She has not been charged with any crime. The only thing she appears to have violated is the terms of the service agreement on sites like facebook -- and everyone's trust. She did, however, offer an apology to the internet community that she betrayed, which taryn posted on her website. Why would somebody do something like this? Why would she make all this up? She didn't profit from it. She did not profit from it. had -- you know, the attention must have kind of been addicting. People who do this, I think, justify it by saying, okay, i know I lied but what is important, it was still me. Reporter: But do you buy that? Do you buy that this is a victimless act? A victimless deception? There's absolutely a victim. To share intimate details of your life and feelings with someone who's deceiving you is wrong. And no one should go through that. Reporter: Do you think we're going to see more of this kind of phenomenon? Absolutely. And so long as we're not looking people in the eye face-to-face, there's always going to be room, a lot of room for deception.
This transcript has been automatically generated and may not be 100% accurate.