Castle raises $9.2 million for AI that protects consumer apps from account takeovers

Castle, a San Francisco-based startup that wants to help businesses keep their customers' online accounts safe from fraud, has raised $9.2 million in a series A round of funding from Index Ventures, with participation from Y Combinator, First Round Capital, F-Prime Capital Partners, and a host of individual angel investors. Founded in 2015, Castle works with web and app developers looking to offer greater security inside their consumer-facing apps. Castle's technology helps prevent all manner of account takeover (ATO) efforts, whether through manual attempts or automated methods, including credential stuffing. In 2017, identify fraud cost 17 million U.S. consumers $17 billion, according to a report by Javelin Strategy & Research, with "account takeover" making up more than $5 billion of the losses. A separate report last year by Shape Security noted that credential stuffing, specifically, costs U.S. businesses around $5 billion a year.