However I'd love if this triggered some comments and questions from people who are interested in this kind of thing.
doing the analysis and cancellations manually in excel, without backtesting, feels super irresponsible (she tested it in production!!)
"How could Jenn be sure that the transactions she was canceling were fraudulent transactions? Jenn anticipated that legitimate customers would complain; however, she never heard from anyone whose transactions were canceled for this reason."
wat
The super-majors like Amazon are heavy into machine learning and rebuild some of their models daily. But even with their prowess they still had a thousand people doing manual investigation a couple of years ago. One subtle signal that you have triggered their fraud system is that they will ask you to renter your card number.