Ronen Bergman and Mark Mazzetti investigate Pegasus, an Israeli spying tool that was acquired for use by the F.B.I., and which the United States government is now trying to ban. Pegasus is used globally. For nearly a decade, NSO, an Israeli firm, had been selling this surveillance software on a subscription basis to law-enforcement and intelligence agencies around the world, promising to consistently and reliably crack the encrypted communications of any iPhone or Android smartphone. The software has helped the authorities capture drug lords, thwart terrorist plots, fight organized crime, and, in one case, take down a global child-abuse ring, identifying suspects in more than 40 countries. But it has been prone to abuses of power: The Mexican government deployed Pegasus against journalists and political dissidents; and it was used to intercept communications with Jamal Khashoggi, a columnist for The Washington Post, whom Saudi operatives killed and dismembered in Istanbul in 2018...