After a hell of a start to the year, another one of Uber’s laundry-list of ethical and legal misdeeds is catching up to the ridesharing app. This time, it’s Greyball, a controversial tool that Uber used to evade cops and competitors in areas where the ridesharing service was not legally allowed to operate.

This month, Uber’s controversial use of the “Greyball” tool was put under a criminal investigation by the Department of Justice. The New York Times first exposed Uber’s Greyball program in March, prompting the company to ostensibly launch an internal review of the program, which it claims was used for a variety of reasons, not just to evade law enforcement or local authorities. But what is Greyball, and how could it affect a normal commuter just trying to find a ride?

What is Greyball?

Greyball is a software tool used by Uber employees. It’s not a part of the app that a regular user could access, rather, it’s a special program or application in the back-end of the service that Uber engineers can access to do certain things. The program collects data from the Uber app, as well as outside sources, and uses that to give Uber engineers specific powers to change how standard users see the app.

Yeah, but What Does It Do?

The biggest thing that Greyball can do is create an entirely different version of the app, like a ghost version of the service. The user would open up the Uber app and see a normal interface of ride options, a map with little car icons, everything else that the app would usually display. But instead of being accurate data, the Greyball version of the app could be controlled by Uber’s engineers. The user might see car icons on the map near them when in reality there were no cars nearby or vice versa — they might not see cars when one was driving right by them. In other words, it let users think they were using the real app, but never be able to catch a ride.

Wait, Why Would Uber Want to Do That?

See, here’s the catch — Greyball wasn’t typically used on everyday users. The company said in a statement to Inverse in March that one reason it was designed was to protect drivers from people looking to harm them. When Uber first started, there were widespread protests against the service, mainly by traditional taxi drivers who thought the app put them out of a job. And occasionally, things got violent. So Uber says it used Greyball, which it’s had in its toolbox since at least 2014, to shut out people who were potentially trying to track down an Uber driver and hurt them. In the United States, however, the app was used for a different purpose — to evade the cops.

From the beginning, Uber has had a reputation for playing fast and loose with the law (see: its unregistered self-driving cars that got kicked out of California for running a red light). When the app was expanding to cities around the U.S., some local legislation actually made the app illegal (usually because of laws around who can and cannot operate a taxi service). But Uber wanted to work in those cities anyway, so it needed a tool to keep away from the cops. Per the Times report from March, Uber engineers in a designated city (take Portland, Oregon for example) would watch the map of users and try to spot the ones that were cops. Often, they’d “eyeball” an area around police stations and city buildings, where regulation enforcement agents worked, and then see who was logging on and off the app. If they thought someone was a cop, they’d flag them for Greyball. They could even go broader, and just draw a digital “geofence” around the whole area, making everyone who tried to use the app from city hall or the local PD get the bogus Greyball version. So when a cop or regulator logged on to try to hail an Uber and ticket the driver/ build a case against Uber, they wouldn’t be able to catch a ride. Check out what it looks like in this video below (spoilers: it looks like a dude standing there trying and failing to get a ride. Bummer.)

What Does This Mean for Me as an Uber User?

Honestly, probably not a lot. If you’re not a cop or a government agent trying to track down an Uber driver, or someone looking to do harm, it’s reasonably unlikely that you’ve been Greyballed. The reason Greyball is significant is more of a matter of precedent and reputation. Whenever you use an app like Uber, you’re trusting the company with an enormous amount of data. How the company then uses that data is between it, the government (i.e. what’s legal and what’s not), and the app’s Terms of Service (which, let’s be real, no one reads). Over the course of a few short years, Uber has used the data provided to it by customers and drivers alike in a variety of disconcerting ways, like the “Hell” program that stalked rival Lyft drivers, the series of psychological tricks it uses to keep drivers working, and the secret program that left code on users’s phones after they deleted the app, which violated Apple’s terms of service and led to a tense conversation between Uber CEO Travis Kalanick and Apple’s Tim Cook. It’s always your choice to use the app, which, realistically, will always be an easy way to get home after a night out on the town or catch a ride to the airport with, but it’s important to know what the company you’re entrusting with your data (and paying money to) is all about.

Ok, So What Happens Next?

Reuters reports that all Uber has received so far is a subpoena. A Northern California grand jury wants documents explaining more on how Greyball worked and how it was deployed, which means that a criminal investigation is underway. But a grand jury subpoena is just the first step, and doesn’t mean that anyone will have to formally testify or that charges will be brought, so there’s a chance that this all blows over. If charges are brought against the company, we’ll know more then.

Photos via Getty Images / Justin Sullivan, Getty Images / Carl Court