The company said this month that it would stop selling in Russia. Equipment and software connecting the government's largest telecommunications network was left behind by the company.
The tool was used to track Navalny's supporters. The phone calls of a Kremlin foe who was later assassinated had been monitored. The System for Operative Investigative Activities, or SORM, is most likely being used at the moment as President Putin purges and silences antiwar voices inside Russia.
According to company documents obtained by The New York Times, SORM was linked to Russia's largest telecom service provider, MTS, for more than five years. The documents show how the SORM system was worked on by state-linked Russian companies. Russia's main intelligence service uses SORM to listen in on phone conversations, intercept emails and text messages, and track other internet communications.
The documents show that the company knew it was enabling a Russian system. The work was essential for the company to do business in Russia, where it had become a top supplier of equipment and services to various telecommunications customers. Even as Mr. Putin became more controlling at home, the business earned hundreds of millions of dollars annually.
Multinational companies capitalized on Russian demand for new technologies. Global outrage over the largest war on European soil since World War II is forcing them to re-examine their roles.
The idea of products and services being compatible has been changed by the conflict in Ukraine. Tech companies used to argue that it was better to remain in authoritarian markets, even if that meant complying with laws written by autocrats. Apple works with a state-owned partner in China to store customer data in order to keep it out of the hands of the authorities. The authorities in China can buy chips from Intel and Nvidia.
The lessons that companies draw from what is happening in Russia could have consequences in other countries where advanced technologies are sold. The America Competes Act, passed by the House of Representatives in February, gave the Commerce Department the power to block companies from selling technology in certain places.
Tom Malinowski was an assistant secretary of state for human rights in the Obama administration.
Without the company's involvement in SORM, it would not have been possible to make such a system, according to an expert who reviewed some of the documents.
Mr. Soldatov is a fellow at the Center for European Policy Analysis.
Under Russian law, it was required that products be made that would allow a Russian telecom operator to connect to the SORM system. The company said that other countries make similar demands and that it must decide between helping make the internet work or leaving altogether. The company said that it did not manufacture, install or service SORM equipment.
The company said it follows international standards used by many suppliers of core network equipment. It called on governments to set clearer export rules for technology and condemns Russia's invasion of Ukraine.
It said in a statement that it does not have the ability to control, access or interfere with any lawful intercept capability in the networks which its customers own and operate.
Requests for comment were not responded to.
The documents that were reviewed by The Times were part of almost two terabytes of internal emails. Some of the documents that were reported on by the cybersecurity firm UpGuard and the news website were linked to the state's snooping on the phone company. The extent of the involvement was downplayed by the company.
The Times obtained a larger cache of information about the program. The documents include correspondence between the company and a Russian firm, photos of the company's work in more than a dozen Russian sites, floor plans of network centers, and installation instructions from a Russian firm.
According to public announcements, after the documents end, Nokia continued to work with Russian telecoms.
SORM is similar to the systems used by law enforcement around the world to wiretap and surveil criminal targets. Telecom equipment makers are often required to make sure that lawful intercept works smoothly within their networks.
In democracies, the police need to get a court order before they can get data from telecom service providers. The SORM system in Russia works like a black box that can take whatever data the F.S.B. wants.
Russia strengthened a law to require internet and telecom companies to give information to the authorities without a court order. The authorities mandated that companies store phone conversations, text messages and electronic correspondence for up to six months and internet traffic history for 30 days. Russia has developed a censorship system that blocks access to websites.
The Russian government has been criticized for using SORM to spy on Mr. Putin's rivals and critics. They said that the system is being used to crack down on dissent against the war. Mr. Putin promised to remove pro-Western Russians from society and his government has cut off foreign internet services.
The pioneer of mobile phones was sold by the company, after Apple and SAMSUNG dominated the market. It makes the bulk of its $24 billion in annual sales by providing telecom equipment and services. The market research firm Dell says that less than 2% of the total revenue of the company comes from Russia and Ukraine.
Telecom equipment providers were legally required to provide a gateway for espionage last decade as the Kremlin grew serious about cyberspying. The Chinese telecom giant was assumed to be willing to do so if they did not get their way.
According to the documents, by 2012 Nokia was providing hardware and services to the MTS network. The schematic of the network that depicted how data and phone traffic should flow to SORM was included in the project documentation. The photos show a cable labeled SORM plugging into networking equipment.
Data would be transmitted to Moscow and F.S.B. field offices across Russia, where agents could use a computer system to search people's communications without their knowledge.
The program's use has been kept secret.
Some information about SORM has been leaked.
The phone calls made by the Russian opposition leader were leaked to the media. Mr. Soldatov said the phone recordings came from SORM. Mr. Nemtsov was killed near the Kremlin.
Mr. Navalny's communications were included in a court case in which they were believed to have been intercepted. Damir Gainutdinov, a Russian lawyer who represented the activists, said that some communications by Mr. Navalny's supporters were tracked by SORM. He said that the authorities merged phone numbers, email addresses and internet protocol addresses with information from the largest social network in Russia to give access to user data through SORM.
Mr. Gainutdinov said that these tools are used to collect data about people and their friends, partners and so on.
SORM was getting international attention. The European Court of Human Rights called the program a system of secret surveillance that was deployed without sufficient protection against abuse. The tools were found to violate European human rights laws by the court.
In the year of 2016 MTS enlisted the help of Nokia to upgrade its network in large swaths of Russia. According to one document, MTS set out an ambitious plan to install new hardware and software between June 2016 and March 2017.
According to the documents, at least 12 cities in Russia have been serviced by the SORM-related work done by the company. In February of last year, an employee of the company was sent to three cities south of Moscow to look at SORM.
The F.S.B. used the SORM hardware manufactured by Malvin. One document instructed Malvin's partners to enter the correct parameters for operating SORM. They were reminded to notify Malvin technicians of their passwords.
Malvin is one of several Russian companies that won lucrative contracts to make equipment. Malvin was one of the companies that was owned by a Russian holding company. The United States, the European Union, Britain and Switzerland have imposed sanctions on Mr. Usmanov because of his ties to Mr. Putin.
Malvin and Citadel did not reply to questions.
The documents specified which cables, routers and ports to use. Network maps show how gear from other companies plugged into the SORM boxes. The company declined to comment.
In Russia, the work related to SORM was often mundane. Orel is a city about225 miles south of Moscow and was assigned to a technician by the phone company.
He was told to carry out work on the examination.
Michael Schwirtz was involved in reporting.