Uber is once again potentially in hot water with US regulators following the disclosure of a program used to track and avoid government officials.
The US Department of Justice (DoJ) has launched a criminal investigation into Uber concerning the Greyball program, software which helped drivers avoid local authorities while remaining on the road.
Greyball, disclosed in March by the New York Times, was a secretive system used to dance around government officials in areas where the ride-hailing service had not been approved.
Created in 2014, the software was utilized in areas including Boston, Las Vegas, Oregon and Paris to "tag" customers believed to be law enforcement or government representatives.
Their accounts would be marked with a small slice of code reading "Greyball," and when the user requested a ride, Uber would serve up a fake version of the app complete with ghost cars to prevent them catching a ride and potentially gathering evidence for use against the company.
Uber would also reportedly conduct user credit card checks to see whether they were linked to organizations such as police credit unions, and even went so far as to provide managers with a guide filled with tactics for use against Greyballed passengers.
Uber confirmed the existence of the program, now defunct for the purpose of tracking law enforcement, but argued that Greyball existed to check ride requests, prevent fraud, and protect drivers.
At the time, Uber said in a statement:
"This program denies ride requests to users who are violating our terms of service. Whether that's people aiming to physically harm drivers, competitors looking to disrupt our operations, or opponents who collude with officials on secret 'stings' meant to entrap drivers."
According to Reuters, a letter sent from Uber's legal team to authorities in Portland, Oregon, claimed the program was used "exceedingly sparingly" in the city before the ride-hailing service was approved in 2015.
The publication's sources say the investigation is still in an early stage and so there is little indication of what potential federal criminal violations or charges might be on the table.
However, Uber has apparently received a subpoena from a Northern California grand jury requesting documents on how Greyball functioned and when it was deployed -- an indication that US regulators are taking the issue seriously.
This is not the only dubious software practice that Uber has been charged with using. Last month, reports surfaced which suggested Apple CEO Tim Cook had to become personally involved after engineers discovered a technique called "fingerprinting" in use by the Uber app, which may have tracked iPhone users even after the app was deleted from their systems. Uber has also been accused of industrial espionage against competitor Lyft by using a tracking software program called "Hell."
ZDNet has reached out to Uber and will update if we hear back.