Christmas gift exchange scam making the rounds on Facebook

A familiar scam is making the rounds on Facebook, just in time for the holidays.

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Authorities have warned the site's users about a "secret sister gift exchange" scam. The scheme is circulated through posts on Facebook in which duped users claim that a person can get up to 36 gifts from other people if they agree to buy a single gift worth $10.

The exchange is a scam and might be illegal, according to police in Cookeville, Tennessee.

"Sounds too good to be true? You're right … it is," police said last year in a post on Facebook. "The gift exchange is a modern version of the chain letter scheme and is illegal."

The U.S. Postal Service warned that the scam and ones like it are "mathematically impossible."

"Do not be fooled … the primary purpose (of the scam) is to take your money," according to the Postal Service.

The scam has been popular on social media for the last few years. Participants are asked to put their names on a list after agreeing to take part -- ostensibly in order to put them at the top of the list for the next batch of secret Santas.

"You have no idea who you're giving that information to, so ultimately what you're setting yourself up for is identity theft," Danville, Pennsylvania, Police Chief Eric Gill warned WNEP last year. "Sending your private information to somewhere where you have no idea where it's going to go is very foolish."

Cox Media Group