For years, the U.S. Justice Department has worked to unravel a global hacking campaign that targeted prominent American climate activists. Now, public tax filings reviewed by NPR reveal an unexpected link between the company that allegedly commissioned the attacks and some of the victims.

The connection emerges as another element in the complex story of how hackers were allegedly hired to attack parts of American civil society. The Justice Department investigation has focused recently on an Israeli private investigator named Amit Forlit whom federal prosecutors are trying to extradite from the United Kingdom for allegedly orchestrating the hacking. Prosecutors say the operation was aimed at gathering information to foil lawsuits against the fossil fuel industry over damage communities have faced from climate change. Sponsor Message

Buried in the investigation's court filings are the names of one of the world's biggest publicly-traded oil companies and one of its longtime lobbyists: ExxonMobil and DCI Group. In an affidavit filed in the UK, a federal prosecutor identifies DCI as the firm that allegedly commissioned the hacking.