NEW YORK (CBSNewYork) – In a third of all marriages, one or both partners admit to cheating.

Now, scam artists are hoping to capitalize on that number by blackmailing spouses.

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As CBS2’s Alice Gainer reported, it starts with a typed letter that arrives in the mail.

“You know, sometimes you get junk mail and just throw it out. This actually seemed like it had been put together by a private investigator or someone who knew what they were talking about,” Dr. Jay Rothkopf said.

The letter threatens “pay me $2,000” or deal with the repercussions of having an extramarital affair exposed.

But how do the blackmailers know about an alleged affair? Actually, they don’t.

“When you look at numbers as to how many people cheat… If they send out 10 letters, maybe there are two or three people who are in fact cheating, and they think they can get them to make a payment,” Dr. Bart Rossi, a psychologist, explained.

It’s the latest scam to make the rounds, and the senders are playing with pretty good odds.

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“What they are trying to do is find someone who is actually most likely cheating, who will then feel guilty and then participate in this… conspiracy,” said Rossi.

The blackmailer instructs the supposed cheating spouse on how to use a digital currency exchange app, so he or she can pay the extortion via Bitcoin.

“It’s an anonymous exchange,” technology expert Ian Marlow explained. “No way to track where the money went or who the money came from.”

Like so many other scams, this one preys on fear by utilizing the U.S Postal Service.

“Our volume of junk mail has significantly gone down over the past number of years. So now when you get something like that that appears legitimate in the mail, we pay a lot more attention,” said Marlow. “If you got that by email, would you pay attention?”

Christine Fuss said her husband has nothing to hide, and the same goes for Rothkopf. But they said they feel for those who might think twice about paying a blackmailer.

“He’s disrupting lives, he’s probably terrified a lot of people,” Rothkopf said.

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The FBI says the details in the extortion letters are just specific enough to make them believable. The agency is now investigating the origin of the letters.