Brett Johnson was still in bed on September 16, 2006, when he heard a knock on the door. He got up, looked through the peephole, but didn't see anyone. He opened the door and walked into the hallway, where federal agents were waiting for him.

"Hey guys, y'all want to come in?" Johnson asked.

"Let's put you in handcuffs first," one said.

Johnson wasn't surprised to see them because he'd spent the past four months on the run. After decades of scamming, he'd been caught using fake cashier's checks and brought in as informant for the Secret Service. He was asked to snoop on former associates who were buying and selling people's personal information on the dark web, according to court documents.

But he continued to steal while working for the government. He used computers at FedEx Kinko's locations to file fraudulent tax returns and route the money to prepaid debit cards.

Federal agents caught on. When they searched his apartment in Columbia, South Carolina, they found 63 prepaid cards inside a sock hidden in a pair of pants in the closet, one fake license, and a bowl with $1,940 in cash at the bottom of a laundry basket, court documents say.

A Secret Service spokeswoman did not respond to a request for comment.

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Johnson says that was when he took off across the country, and was put on the Secret Service's Most Wanted list. He filed fake tax returns while on his way from Texas to California, to Las Vegas, and finally to a condo in Florida where he was arrested.

It wasn't just tax fraud. Before becoming an informant, Johnson says he created fake credit cards with stolen account numbers and opened bank accounts in other people's names. He ran a website called Shadowcrew, one of the first marketplaces for stolen personal information and taught other criminals how to take over people's accounts.

Johnson pleaded guilty to charges of fraud in 2007. He was ordered to pay $332,080 in restitution to victims and sentenced to six years in prison.

Now, he does fraud consulting -- something he used to tell people he did for a living when he was committing crimes himself.

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Johnson says he never thought about the victims, and how they may have needed their tax refund to make rent that year. He didn't think about how many hours they'd have to spend on the phone with the credit card company to prove it was someone else who spent $500 on dinner or bought that Rolex.

"The Internet provides the anonymity and allows you to create this extra persona that you don't consider is real life. But really you're an asshole either way, and I didn't think that at all until I served time," he said.

Johnson told CNNMoney that running scams had been a part of his life since his parents got divorced when he was 10 years old and. He started stealing food, then clothes, and then books.

As he got older, he says he started scamming people on eBay by selling fake merchandise like baseballs with forged Sammy Sosa autographs. When a royal blue elephant Beanie Baby named Peanut started selling for $1,500, Johnson bought gray elephants, dyed them blue, and passed them off as the real Peanut.

It was during college that Johnson says he quit his day job, turning to cybercrime to pay the bills and buy gifts for his soon-to-be wife. They were both in school, and Johnson found it easier to make money this way. He says he financed his first wedding by faking a car accident and claiming the insurance payout at age 24.

"There's three reasons why people commit cybercrime: status, ideology, or cash. Mine was cash -- and the love I could buy with it," Johnson said.

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When he became an informant for the Secret Service, he says he kept stealing to make sure his then-girlfriend would stay with him. He bought her expensive shoes and purses and they went out for extravagant dinners.

"If I wasn't dating anyone, I didn't really break the law. I always justified it because I was doing it for my family, my sister, my girlfriend, my wife," he said.

When he was first thrown in jail, Johnson said he had every intention of getting out and going back to his criminal ways. But by the time he was released in 2011, he had changed his mind.

The terms of his probation tested him. He couldn't get a job that required him to use a computer, a court document confirms. So he started mowing lawns and borrowed money from family. Things turned up when he met a new girlfriend on a dating site. He told her about his criminal history upfront, and it didn't scare her away.

But eventually, he stole again and ended up back in jail for 10 months. She stuck with him and they married after he was released.

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He began landing speaking gigs with help from some in the anti-fraud industry like Neal O'Farrell. He's the Executive Director of the Identity Theft Council and met Johnson about a year ago at a conference.

"You're never fully certain guys like this are completely reformed. But I've always believed you can learn something from the bad guys," O'Farrell said.

Johnson said he's now financially solid, but it took a while to get back on his feet. It wasn't until recently that he became certain himself that he wouldn't be going back to stealing.

"I had been prepping stuff without pulling the trigger, until this summer. I don't plot anymore or scheme. I won't be breaking the law anymore" he said. "I'm not one of the good guys now. But I'm trying to be better."