Former penny-stock broker Jordan Belfort spent nearly two years in prison for scamming investors. Bitcoin, he has no doubt, is the next trap that could leave some retail investors penniless.

"I was a scammer. I had it down to science, and it's exactly what's happening with bitcoin," he told CNBC in a documentary airing Monday. "The whole thing is so stupid, these kids have gotten themselves so brainwashed."

Belfort ran an over-the-counter brokerage house on Long Island called Stratton Oakmont, and pleaded guilty in 1999 to manipulating investors into buying stocks that eventually turned out to be worthless. The former broker's story was depicted by Leonardo DiCaprio in Martin Scorsese's "Wolf of Wall Street."

In order to manipulate markets, Belfort highlighted the need for demand. "Back in the day" he had an army of people calling around the country and the world persuading people to buy stocks he would later "dump" and profit off of.

In the internet age, that manipulation tactic has become easier. Cryptocurrency fundraising known as initial coin offerings in many cases turned out to be frauds and have become the target of Securities and Exchange Commission investigations. Google, Facebook, and Twitter have outlawed advertising of ICOs on their platforms.

"This thing is going to evaporate like a mirage," Belfort said. "There's a lot of really honest people who are going to get slaughtered."