Nokia said this month that it would stop its sales in Russia and denounced the invasion of Ukraine. But the Finnish company didn’t mention what it was leaving behind: equipment and software connecting the government’s most powerful tool for digital surveillance to the nation’s largest telecommunications network.The tool was used to track supporters of the Russian opposition leader Aleksei A. Navalny. Investigators said it had intercepted the phone calls of a Kremlin foe who was later assassinated. Called the System for Operative Investigative Activities, or SORM, it is also most likely being employed at this moment as President Vladimir V. Putin culls and silences antiwar voices inside Russia.For more than five years, Nokia provided equipment and services to link SORM to Russia’s largest telecom service provider, MTS, according to company documents obtained by The New York Times. While Nokia does not make the tech that intercepts communications, the documents lay out how it worked with state-linked Russian companies to plan, streamline and troubleshoot the SORM system’s connection to the MTS network. Russia’s main intelligence service, the F.S.B., …
