Chain letters of the Secret Sister variety are jammed through your front door. You could in theory receive one of these anywhere from Reddit and Facebook. For whatever reason, Facebook seems to be the scammers favourite place to get the ball rolling on this particular scam. Chain letters are essentially pyramid schemes. Pyramid schemes involve funneling money from bottom to top of the pyramid, benefiting those at the top and not many others. For everyone else, youre probably going to lose out.”]
Source: https://blog.malwarebytes.com/cybercrime/2018/11/secret-sister-scam-returns-time-christmas/