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John Mark Moore's in-laws didn't suspect a thing. Not even when Moore repeatedly forged their signatures. According to the U.S. Attorney's Office, the couple, two well-respected California farmers, had no clue their son-in-law was increasing their business lines of credit so he could draw down millions in loans—for himself.
At the same time, Moore persuaded his in-law's friend and business associate—known in court documents only as GLM—to invest more than $12 million in a series of ranching and farm ventures that never materialized.
(Read more:Famous fraudsters, con artists and scammers)
Moore, convicted of fraud, will begin a hefty prison sentence this November. But the story is cautionary: When a scam slams you, you'll never even see it coming. And a new report suggests that Americans may be more vulnerable to fraud than they think. A 2013 report from the Financial Industry Regulatory Authority (FINRA) Investor Education Foundation shows just how susceptible we really are.
"Even with all the attention paid to recent frauds like the Madoff scheme," said Gerri Walsh, president of the FINRA Investor Education Foundation, "we're still seeing investors solicited in high measure—and they are not able to recognize the classic red flags!"
What qualifies as a red flag? Interest rates that are too good to be true—like 2 percent a day. (According to FINRA, 2 percent a day would turn $10,000 into about $1.4 million in just one year!) "Guaranteed" investments. And the most appealing red flag tested: Outperforming the Dow Jones!
FINRA's fraud susceptibility research reveals some surprising facts. For example, the more educated and wealthier you are, the more likely you are to invest in a potentially fraudulent scheme. And men, because they are generally less risk averse, are more vulnerable than women.
Other findings are sad but not so surprising: Americans over 65 years of age are 34 percent more likely to lose money to fraud than their under-50 counterparts.
(Read more:Worst states for mortgage fraud)
Of course, it's especially hard to spot fraud when it comes from someone you trust. A family member or a friend, or perhaps someone from your church or Facebook tells you about a great investment. Everybody's getting in on it! Or maybe it's a loved one just asking for help: a loan. It all seems upfront and good … until you find out you've been scammed.
One in 6 respondents to the FINRA study said they had suffered a significant financial loss by being taken advantage of by a family member. Fraud and loss courtesy of friends runs at about the same rate. And 34 percent of respondents who had lost money in a fraud were introduced to the seller through a friend; 8 percent were introduced to the seller in a social situation.
Victims of fraud perpetrated by a family member are more likely to have modest incomes. Such were the relatives of master fraudster John Ruffo. As reported by CNBC's "American Greed: The Fugitives," even after Ruffo got caught defrauding seven banks out of $350 million, he wasn't finished breaking hearts. Next, he turned to his relatives.
"He was really good at keeping secrets," Ruffo's ex-wife, Linda Lausten, told "American Greed." When bail was set at $10 million, Lausten, his elderly mother and five of his aging aunts and uncles put up their homes as collateral. "There are all these little people, elderly people, so innocent and naïve," said Lausten. "And we just signed away everything."
(Read more:Mortgage fraud: What you need to know)
Two years later, Ruffo, convicted and sentenced to 17 years in federal prison for the biggest bank fraud of the decade, failed to surrender to serve his sentence. He ran—knowing his wife, mother and relatives would all forfeit their homes. His mother died in a nursing home; she never saw him again.
Even Ruffo's attorney couldn't believe the extent of Ruffo's treachery. "To this day," Judd Burstein told "American Greed," "it astounds me that somebody would do something like that and that to me is really pure evil."
"It was a very selfish act," Deputy U.S. Marshal John Noel told CNBC. Ruffo is still a fugitive, and Noel, the case agent, is still searching for him. "I wish I could give it 110 percent of my time."
For anybody who cares about investing, protecting yourself from skillful hucksters can be tough. "Fraudsters who are 'good' at their game will put you into a heightened emotional state," said Walsh. They talk excitedly and create a feeling of pressure. "They aim to move you from the rational side of your brain to the emotional side."
Slow down, advises Walsh. "Don't make snap decisions. Ask questions to take charge of the conversation." And above all, said Walsh, stay rational.
—By Celia Watson Seupel, Special to CNBC
CNBC follows the money trail in search of the most wanted white-collar fugitives."American Greed: The Fugitives" airs Thursdays at 10 p.m. EDT.