Financial fraud has been around for centuries, destroying the lives and fortunes of countless victims around the world. But the most recent crop of con artists has an advantage that Charles Ponzi and even Bernie Madoff never dreamed of: social media. It may be the most effective tool for fraudsters since money itself.

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“I wouldn’t say it’s changed the nature of fraud in America, but it’s definitely made it more accessible to the average person,” author and social media expert B.J. Mendelson told CNBC’s “American Greed.”

Take the case of Anna Delvey, who had much of New York society convinced she was a German heiress, a fashion icon and an up-and-coming entrepreneur. Former Vanity Fair photo editor Rachel Williams was among those taken in, and she told “American Greed” that Delvey’s social media accounts were a big reason.

“I had seen Anna in photos on Instagram and saw that she had over 40,000 Instagram followers,” Williams said. “She had a lot of artsy photos of travel and art and shopping, pictures with people in the fashion world.”

The two became fast friends. Indeed, Anna had lots of friends in high places, and she managed to get many of them to pay for a lavish life of parties, high fashion and international travel. She even came tantalizingly close to securing more than $20 million in credit from a big New York bank to create an arts and social club to be called “The Anna Delvey Foundation.”

Her flashy lifestyle and legions of social media followers notwithstanding, Anna was not Anna Delvey. She was Anna Sorokin, born in Russia. And while she did come to the U.S. from Germany, where her family had moved when she was a teenager, she was no heiress. She was a criminal. A New York jury convicted her on five out of seven criminal counts, including theft of services and attempted grand larceny. A judge sentenced her last year to four to 12 years in prison.

What is it about social media that so effectively supercharges frauds by Sorokin, aka Delvey, and so many others? Mendelson said it is a function of human nature.

“The way our brains are wired, we’re not set up to look for fraud,” he said. “If something looks like a duck and quacks like a duck, more often than not, it’s a duck, at least that’s what our brain tells us.”

Mendelson, author of the book “Social Media is Bulls—,” said platforms that rely heavily on images are especially tricky because of our trusting nature.

“We’re very visual creatures. We’re more likely to take in information, and unless something seems really off, we’re more likely to believe it,” he said.

To protect yourself, put the images that you see on Instagram and other visual platforms through a reverse image search, pasting or uploading the picture into Google or your favorite search engine.

“A lot of fake accounts will generally want to ‘populate,’ which means fill out their account with content, and what they do is they steal imagery from all sorts of places,” Mendelson said. “You can do a reverse image search to see if that image was stolen.”

Regardless of the platform, Mendelson cautioned against merely looking at the number of followers. Consider how the social media figure interacts with them.

“If they have a million followers, but only 10 people are interacting with all their posts, that should be a serious red flag. That can mean that there’s bots. That can mean it’s just a spam account of some other kind,” he said.

Next, check to see what those followers say. Look for the telltale signs that the followers are not real.

“The most common one is it just says ‘thanks’ over and over and over again. Or it’s just a short sentence that’s repeated in every comment that they leave on people’s profiles,” he said. “That’s usually the work of either a bot or someone that was hired to populate the account.”

And if you interact with the account yourself, beware of someone who is too responsive.

“If you message someone and they message you right back at, like, 3 o’clock in the morning, that should be a sign that maybe something is not legit with that account,” Mendelson said. “Maybe someone overseas is piloting that account and it’s not actually based in the United States.”

Fraudsters do not only use their own accounts to pull off their scams. They also use yours. Beware of the information you share in your social media posts, or in posts that you respond to such as those Facebook questionnaires asking about various aspects of your life. You could be giving away the keys to your identity, your passwords, even your home.

“If you’re going on vacation don’t share it,” Mendelson said. “You can share it after you come back from your vacation, but what happens is there’s all sorts of schemers and fraudsters who might be looking for people that are away, and if you’re away, you could be robbed.”

Things can be especially tricky on professional platforms like LinkedIn. Identity thieves troll those sites looking for information.

“If you put on LinkedIn that you were at SUNY Potsdam from 2004 to 2006 and you log into your mortgage account and one of the security questions is, ‘What college did you attend?’ that person is one step closer to breaking into your account,” Mendelson said

Make sure your privacy settings prevent strangers from viewing your personal information, and do not connect with people you do not know. When setting up your security questions on websites that require it, be careful not to provide information that a hacker can also find on your social media pages.

“The more information someone has on you, the easier it is to steal your identity,” Mendelson said.

The social media landscape is filled with influence, both real and manufactured. While some posts seem to magically go viral, companies pay millions to social media figures—known as “influencers”— to plug their products.

The practice can be perfectly legal, of course. But Mendelson warned not to get taken in by manufactured hype.

“Anyone can be an influencer and that’s the problem,” he said. “You can certainly fake it until you make it. You can certainly create a persona of some kind that fits within some kind of niche and then have brands come to you that want to give you money.”

To guard against being unduly influenced, Mendelson said people should use their head when they use the internet.

“When you use Instagram, when you use Twitter, you’re looking at your phone. You’re in the middle of other things. We know our brains can’t multitask, so you’re very susceptible to falling for all sorts of hoaxes,” he said. “So, as cheesy as it sounds, stop and think and fact-check if you really need to. Google is your friend.”

Without a little skepticism, he said, you run the risk of going the route of Delvey’s victims.

“She looked the part of this wealthy heiress that was living the lifestyle,” he said, “because when it comes to imagery, we’re very easily fooled, that’s all you really need to do, is look the part.”

See how Anna Sorokin transformed herself into “heiress” Anna Delvey and lived the high life at other people’s expense. Catch an ALL NEW episode of “American Greed,” Monday, Feb. 24, 2020, at 10 p.m. ET/PT only on CNBC.