Greyball is a software tool used by the ride-hailing service Uber to identify and deny service to certain riders, including riders whom Uber suspects of violating its terms of service. Uber's use of Greyball was made public in a March 3, 2017, investigative report by The New York Times, which described how, as early as 2014, Uber had used Greyball to evade local government authorities in the United States, Australia, South Korea, and China. In the days following the publication of the New York Times story, Uber admitted that it had used Greyball to thwart government regulators, and it promised to stop using the tool for that purpose.
Development and use
Uber reportedly developed Greyball to identify individuals who Uber suspected of using its service improperly, and it began using the tool as early as 2014. 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 claimed that it used Greyball to deny service to individuals suspected of violating the company's terms of services, such as people seeking to harm Uber drivers, disrupt Uber operations, or carry out law enforcement actions against Uber drivers. However, after The New York Times revealed Greyball's existence in March 2017, Uber said it would stop using it to evade local government regulators.
According to the New York Times report, which was based on interviews of four current and former Uber employees and a review of internal Uber documents, Greyball used several methods to identify and deny service to government officials who were investigating Uber for violations of local laws, especially when Uber moved into a new city. Those methods included:
- Geofencing. Uber would create a digital map that identified the locations of city government offices. If a potential rider attempted to hail a ride from the area around a government building, Greyball would flag the individual as a possible law enforcement agent.
- Mining credit card databases. If Uber identified a credit card as being associated with a government agency or police union, it would flag that individual in Greyball.
- Identifying devices. Since government agencies would often buy cheap cellphones for use in sting operations, Uber employees would visit electronics stores to obtain device numbers for inexpensive phones and input those device numbers into Greyball.
- Searches of social media. Uber employees searched social media profiles to identify possible law enforcement agents. Uber then flagged those individuals in Greyball.
- Eyeballing. Greyball would determine if a potential rider had been opening and closing the Uber app numerous times without calling for a ride. This was especially used in conjunction with Geofencing to detect official monitoring.
U.S. Department of Justice investigation
In May 2017, several news organizations reported that the United States Department of Justice had opened a criminal investigation into Uber's use of Greyball to avoid local law enforcement operations. The Department of Justice initially focused on Portland, but the inquiry was expanded to include Philadelphia.
City of Portland investigation
On March 6, 2017, the City of Portland, Oregon announced an investigation into whether Uber had used Greyball to obstruct the enforcement of city regulations. The investigation by the Portland Bureau of Transportation (PBOT) found that:
When Uber illegally entered the Portland market in December 2014, the company tagged 17 individual rider accounts, 16 of which have been identified as government officials using its Greyball software tool. Uber used Greyball software to intentionally evade PBOT’s officers from December 5 to December 19, 2014 and deny 29 separate ride requests by PBOT enforcement officers [...] In using Greyball, Uber has sullied its own reputation and cast a cloud over the [Transportation Network Companies] industry generally.— Transportation Network Companies: Regulation Evasion Audit, Portland Bureau of Transportation, Report Summary, April 28, 2017
Following the release of the audit, Portland's commissioner of police suggested that the city subpoena Uber in order to force the company to turn over information on how Uber used software to evade regulatory officials.
Transport for London ruling
Transport for London cited the use of Greyball in London as one of the reasons for its decision not to renew Uber's private hire operator licence. The decision stated that the way in which Uber used Greyball contributed to it failing to meet the standards of a "fit and proper" private hire operator. Consequently, Uber would not be able to operate legally in London after its licence expired on 30 September 2017 unless they entered an appeal within 21 days. Uber's appeal against the ban was heard at Westminster magistrates' court on 25 June 2018. 
- Joe Sullivan, Chief Security Officer at Uber (March 8, 2017). "An update on "greyballing"". Uber. Retrieved April 30, 2017.
- Isaac, Mike (March 3, 2017). "How Uber Deceives the Authorities Worldwide". The New York Times. Retrieved April 30, 2017.
- della Cava, Marco (March 8, 2017). "Uber admits its ghost driver 'Greyball' tool was used to thwart regulators, vows to stop". USA Today. Retrieved April 30, 2017.
- Timberg, Craig; Fung, Brian (March 3, 2017). "Uber's secret 'Greyball' program shows just how far it will go to get its way". Chicago Tribune. Retrieved April 30, 2017.
- Somerville, Heather (March 8, 2017). "Uber prohibits use of 'Greyball' technology to evade authorities". Reuters. Retrieved April 30, 2017.
- Levine, Dan; Menn, Joseph (May 5, 2017). "Exclusive: Uber faces criminal probe over software used to evade authorities". Reuters. Retrieved May 5, 2017.
- Dwoskin, Elizabeth; Timberg, Craig (May 4, 2017). "Justice Department opens criminal probe into Uber". The Washington Post. Retrieved May 5, 2017.
- Isaac, Mike (May 4, 2017). "Uber Faces Federal Inquiry Over Use of Greyball Tool to Evade Authorities". The New York Times. Retrieved May 5, 2017.
- Isaac, Mike (May 5, 2017). "Justice Department Expands Its Inquiry Into Uber's Greyball Tool". The New York Times. Retrieved May 6, 2017.
- Njus, Elliot (March 6, 2017). "Portland to investigate Uber's 'Greyball' scheme to thwart regulators". The Oregonian. Retrieved April 30, 2017.
- "Transportation Network Companies: Regulation Evasion Audit". Portland Bureau of Transportation. April 28, 2017. Retrieved April 30, 2017.
- Njus, Elliot (April 27, 2017). "Portland may subpoena Uber over regulator-dodging 'Greyball' software". The Oregonian. Retrieved 30 April 2017.
- "TFL decision on Uber London Limited". TfL. Transport for London. September 22, 2017. Retrieved September 22, 2017.
- "Uber has lost its licence to operate in London". Business Insider. September 22, 2017. Retrieved September 22, 2017.
- "Uber to begin appeal over London licence". BBC News. 2018-06-25. Retrieved 2018-06-25.