For many, the holiday season is the happiest time of the year — especially for online scammers. They’ve returned with one of their most successful Christmas scams, the “Secret Sister” gift exchange, police say.

The scam, which appears on Facebook, asks for “six ladies to participate in a Secret Sister gift exchange.” In return for mailing a $10 gift to a “secret sister,” a participant gets between six and 36 gifts in return, the ad promises. Needless to say, the gifts never arrive. According to the Better Business Bureau, “This is a typical pyramid scheme. Pyramid schemes are illegal if money or other items of value are requested with assurance of a sizable return for those who participate.”

The Better Business Bureau is reminding people that emails or online posts that promise a big return for a small investment never pan out, and you’re breaking the law if you pass on the message to other users. The best thing to do is simply ignore them, police say.