The chain letter used to be just that, letters physically sent through the mail but they turned out to be what is casually referred to as a pyramid scheme. The age of social media hasn't stopped the practice and one notorious scam is still out there just in time for the holiday shopping season.

The "Secret Sister Gift Exchange" is popping up on Facebook again and authorities want to reiterate the the risk with falling for the scam.

The pitch goes like this:

"The Secret Sister gift exchange is back! I'm looking for six women who would be interested in a pre-holiday gift exchange. You only have to buy one $10 gift and send it to your secret sister. You will then received 6-36 gifts in return. Let me know if you're interested and I will send you the information for your secret sister. We all could use some happy mail!"

Obviously, the use of email and social media can cause the chain to spread faster. The US Postal Service has clear regulations against pyramid schemes. Facebook could also block an account because the user's personal information is involved because it goes against their terms of agreement.

In other words, if you see a post with the words "secret sister" or "gift exchange" in it, avoid it at all costs.