Avoiding Fraud Hunt's team was responsible for protecting Citigroup from fraud and bad investments. She and her colleagues inspected loans Citi wanted to buy from outside brokers and lenders to see whether they met the bank's standards. The mortgages had to have properly signed paperwork, verifiable borrower income and realistic appraisals. Citi would vouch for the quality of these loans when it sold them to investors or approved them for government mortgage insurance. Investor demand was so strong for mortgages packaged into securities that Citigroup couldn't process them fast enough. The Citi stamp of approval told investors that the bank would stand behind the mortgages if borrowers quit paying. At the mortgage-processing factory in O'Fallon, Hunt was working on an assembly line that helped inflate a housing bubble whose implosion would shake the world. The O'Fallon mortgage machinery was moving too fast to check every loan, Hunt says.