Uber developed an internal software tool called Greyball, which uses data collected from the Uber mobile app other means, to avoid giving rides to certain individuals. The tool was used starting in 2014. By showing "ghost cars" driven by fake drivers to the targeted individuals in the Uber mobile app, and by giving real drivers a means to cancel rides requested by those individuals, Uber was able to avoid giving rides to known law enforcement officers in areas where its service is illegal. Investigative journalism by The New York Times and the resulting report, published on March 3, 2017, made public Uber's use of Greyball since 2014, describing it as a way to evade city code enforcement officials in Portland, Oregon, Australia, South Korea, and China.  At first, in response to the report, Uber stated that Greyball was designed to deny rides to users who violate Uber's terms of service, including those involved in sting operations.  According to Uber, Greyball can "hide the standard city app view for individual riders, enabling Uber to show that same rider a different version". Uber reportedly used Greyball to identify government officials through factors such as whether a user frequently opens the app near government offices, a review of social media profiles by Uber employees to identify law enforcement personnel, and the credit cards associated with the Uber account.