If they do, they are told they will send out one gift but will receive 36 back from anonymous people – hence the name “secret sister” – seemingly making it an obviously good idea.

If a stranger on the internet promises you a Christmas gift for a $10 buy-in and some personal information, it probably isn't legit, the Better Business Bureau warns.

One Facebook post published earlier today, read: "Doesn't matter where you live —you are welcome to join. You have to buy one gift valued of at least $10 and send it to your secret sis.