A secret Uber program internally dubbed “Hell” allegedly spied on arch-rival Lyft to determine which drivers were working double shifts for both companies, letting the cab-hire app steer more work towards them in an attempt to deprive its competitor of workers.

The report of the “Hell” program continues a string of uncomfortable claims for the company, still dealing with the fall-out of a string of sexual harassment allegations at the beginning of the year, and now operating with a brand new head of public policy and communications following the departure of its previous PR chief, Rachel Whetstone, on Tuesday.

The program, which was run between 2014 and early 2016, used a flaw in Lyft’s rider app to track drivers, according to US news site the Information. When a Lyft rider requests a cab, the app reports up to eight nearby drivers, using their driver IDs for each one. Those driver IDs are fixed and unique, allowing Uber to write a program which spoofed the Lyft app, repeatedly requesting rides in various segments of various cities, to find out which drivers were working where.

By harvesting the data for long periods, Uber was able to build up detailed profiles of individual Lyft drivers, the Information reports, eventually allowing it to match multitasking workers to its own driver profiles.

That information allowed it to attempt to cut Lyft off at the knees in cities where competition for drivers was fierce, according to the Information. By artificially ensuring that double-shifting drivers were given more Uber rides, the company allegedly attempted to limit the driver availability for its competitor. In some cities, where as many as 60% of drivers work for both companies, that could be the difference between breaking even and operating at a loss in the ultra-slim-margin industry.

The “Hell” program – so called in contrast to Uber’s controversial “Heaven” or “God View” program, which allows employees to see a view of all Uber drivers and passengers operating in any given city – was reportedly run in a top-secret manner. Only a few employees were aware of its existence, with even city-specific general managers not informed of how the data on Lyft drivers was obtained.

In early 2016, the program was allegedly discontinued as a result of Uber’s competitive focus shifting from beating Lyft in the US market, to making inroads to emerging economies like India and China (where the company eventually sold out to local cab-sharing firm Didi Chuxing).

For a long time, the company’s feud with Lyft was tied with its endless squabbles with national and local regulators as its biggest source of scandal. In 2014, the Verge alleged a plethora of techniques used to sabotage its rival, including requesting then cancelling rides using burner phones and pre-paid credit cards, as well as pitching Lyft drivers mid-trip to switch their allegiance. Uber denied the claims.

But as the war has died down, Uber has still had to deal with other crises. It is currently in the midst of a sexual harassment investigation prompted by a blogpost from a former employee, even while it continues to fight regulators when it expands into new cities and services. And ticking under its entire business model is a long-running dispute about the nature of its relationship with its own drivers: whether they are considered employees, contractors, or workers has enormous implications for how long its disruptive model can last in the real world.

Uber has not replied to a request for comment.