The "Secret Sister" scam is making the rounds on Facebook again this year, here's what you need to know.

The scam goes something like this -- you see a post on Facebook inviting you to be a part of a gift exchange where you're supposed to get 36 gifts back, providing you contribute a $10 or $15 gift first.

WIVB reports that the scam is illegal, "United States Post Office regulations are very clear about pyramid schemes, and these gifts are being sent through the mail."

The U.S. Postal Inspection Service explains, "Chain letters are a form of gambling, and sending them through the mail (or delivering them in person or by computer, but mailing money to participate) violates Title 18, United States Code, Section 1302, the Postal Lottery Statute. (Chain letters that ask for items of minor value, like picture postcards or recipes, may be mailed, since such items are not things of value within the meaning of the law.)"

So if you see this posted on Facebook, know it's a scam and move along.