Transcript for Army veteran had his image stolen and used to scam women online
Reporter: He might appear in your inbox as a handsome army medic serving on a peacekeeping mission overseas, and he might even tell you about life back home on his farm. You can make up a lot of good stories with a guy in a uniform, a kid on a horse. Reporter: But the man in the photos, Brian Denny, isn't the same person in the keyboard. There were double digits in fake accounts that came up. Reporter: He's the victim of a bizarre case of identity theft. His pictures plastered across dozens of social media platforms. Facebook, Instagram, linked in, tinder, just to name a few. Reporter: Even a Chinese site. Apparently. Reporter: A retired colonel, he has found himself immersed in the shady world of online romance fraud when he found his photo had been stolen and used to lure women all over the globe into thinking they're in a relationship with him. When did you first become aware your identity had been stolen? I got a note on linked in saying I have been talking with someone who says they're you. She met me through social media and this guy had been, she had sent him money for airline tickets. Reporter: Did he come and visit? He did not. Reporter: It didn't take long for Brian to realize this was more than just a one-of. There's more than 3,000 accounts on Facebook alone. Reporter: More than 3,000. That's right. Reporter: Soon the messages were pouring in. Hi, I'm a doctor from Kosovo, and I think I've been scammed. I'm sorry to disturb you. Hello, someone got pictures of you. Reporter: And two and a half years later they haven't stopped. You end up breaking up with someone every week, and I say breaking up with them because they've committed not just emotionally been financially. It really becomes overwhelming to be the bearer of bad news all the time for folks. Reporter: The real Brian Denny is oo husband, father and proud veteran. I'd like to say hi to all our friends and family and supporters. Reporter: Someone who has spent a lifetime fighting for others. The fake Brian Denny, well, he could be anyone. I've been everybody from frank Smith to Scott Glen to Ricardo. Sergeant, colonel, major. I'm a leading humanitarian assistance mission in Iraq, Afghanistan, I'm in all those places doing all those things. Reporter: How much money has been taken from these various women in your name? There's been a couple hundred thousand. Probably my biggest contributors have been from Australia where the total for three ladies is pretty close to $200,000 alone. Reporter: Internet crime is a big business, but unlike many criminal enterprises online, the world of romance scamming doesn't exist on the edges of the darkweb. Get your photos at low cost. Reporter: Facebook groups like these ones trafficking stolen information out in the open. Free fake profile so you look legit and European. Reporter: And on community forums which actually teach people how to create fake profiles. Instagram account for sale, 950-plus followers. Reporter: And lure clients, even facilitate money laundering. These posts are really bold. I mean, they put out on sites. They don't think they're going to be caught, clearly. But our take on that is yes, you will. Reporter: Amy Hess works with the FBI. She says as social media has become more popular, these cases called confidence frauds, have become much more prevalent. Are they committing any kind of crime by doing this? As soon as we can connect them to actual crime, yes, they are and have been targets of our investigations. Reporter: Is it hard to chase? It is sometimes. It's a very complex fraud. There's a criminal network operating. There's multiple people. Sometimes they have the victim be part of that either in a witting or unwitting capacity to be part of that network because they're moving money for them. Reporter: Money laundering. This is a billion dollar business? I would say with confidence, it's in the billions of dollars. Each one of those is a person. Each one of those is a victim. Those are people's life savings. Reporter: People like Julie how much did you lose? Between $400,000 and $500,000. Reporter: Julie was looking for love when she turned to online dating, and it didn't take long for her to develop a relationship with a man who said his name was mark. He was a very, very good-looking man. I was attracted to him. Reporter: Mark told Julie he was working overseas. The two would e-mail and talk on the phone for hours at a time. But Julie says she was surprised when mark made a request for money. $500. Reporter: Soon Julie was out of hundreds of thousands of dollars all to a man who was not who he said he was. Describe to me the home when you realized -- Crushing. Absolutely crushing. I was suicidal. I cried a lot. Reporter: Have you ever found out who the real mark is? No. Tried but never have. Reporter: For Brian, the battle against online scammers is deeply personal. Every day that it continues to go on there's some other person that's going to give their life savings, some other person is going to be heartbroken. Reporter: This has to be tough on your wife. You're getting messages daily, weekly, from these women who think they have a love affair going. This is a tough issue. Reporter: I can see why you want to put a stop to it. My family wants nothing to do with this. Reporter: A quick search on Instagram or Facebook still turns up dozens of active profiles using his name and why are members of the military such a popular target? We highly value our military personnel, so it's an added level of respect, an added level of reverence that we place on them. The person who is perpetrating this fraud never wants to meet you. So they have to come up with a reason why they can't meet you. For one, they're in the military. They're in some type of business that would keep them constantly traveling. Reporter: Why not just completely disengage. Right. Reporter: From being online or on any type of sites? It only makes it easy for the criminals to operate. There will be someone else whose picture is used to do this. Reporter: So you will not pull away. No, will not do it. Reporter: He has taken the case up with Facebook where he has found the highest concentration of fake profiles with Kathy waters. The duo met after her friend was scammed by someone using Brian's photos. Together they started a group advocating against romance scams, submitting a lengthy report to Facebook about what they say are major platform they also lobbied to congress. You've met with Facebook. Mm-hm. Reporter: Are you satisfied with what you got from Facebook? We've had a couple meetings. No changes are going to happen without Facebook's cooperation. Reporter: But people like you are having their identity stolen. Other people are losing hundreds of thousands of dollars. Yeah. Reporter: There are crimes being committed here. Right on their platform. And they don't want the responsibility of determining what's a crime and what's normal social communication. Reporter: In a statement to ABC news, Facebook said impersonation violates our policies and has no place on Facebook. We've developed technology to specifically combat impersonation and will continue to make improvements. We are thankful to Brian and Kathy for working on this issue with us. As a result of our investigation, Facebook removed those groups we flagged to them, telling us they were in violation of the platform's community standards. For Bryan, any action or legislation is too little too he just hopes to serve as a cautionary tale to others lured into a false sense of security on social media. His fight is far from over. So if there's a woman watching this interview right now and she thinks she's communicating with you, colonel Bryan Denny, what do you say? She is not, she is not. It's all fake. It's all made up. It's all a lie. Reporter: For "Nightline," Kyra Phillips in williamsburg, Virginia.
This transcript has been automatically generated and may not be 100% accurate.