MOSCOW >> The must-have accessory at the 2018 World Cup is a passport-sized badge of honor that, for many fans, symbolizes the fulfillment of a lifetime’s ambition.

The badge, called a Fan ID, is an innovation introduced at the World Cup for the first time and is almost as valuable as a ticket. No fan can get into a World Cup stadium without one. It also grants access to perks like visa-free entry into Russia, free transport in and occasionally between host cities and discounts in certain shops and restaurants.

Part identity card and conversation starter, it hangs from a FIFA lanyard around the neck of nearly every fan at the World Cup — a laminated credential to what could pass for the world’s coolest business conference.

Yet it has also raised concerns about privacy in a country that has been a base for international hackers and with a long history of closely monitoring its citizens. Russian authorities said the only purpose of the badges is to improve the security and comfort of fans. However, the badges do give World Cup organizers and security officials the ability to track the location of fans during the tournament and provide them with those fans’ personal information.

Many spectators simply like them as keepsakes.

“I’m going to keep this for the rest of my life,” said Brazilian fan Arnaldo Ylem, 50, proudly looking down at his Fan ID. It displayed a small photo of his face as well as his name in both English and Russian script.

Russian authorities created the Fan ID program as part of an extensive security operation for one of the biggest groups of foreign tourists it has received.

Each Fan ID is logged by Russia’s Communications Ministry under a set of agreements with FIFA, world soccer’s governing body. Organizers said Friday that the Russian government had agreed that all information they obtain, which includes names, dates of birth, passport numbers, phone numbers, emails and home addresses, would be “strictly confidential.”

In total, more than 1.6 million Fan IDs have been distributed to tournament visitors, including VIPs and celebrities. Even the disgraced former president of FIFA, Sepp Blatter, who is attending the event as a guest of President Vladimir Putin, and Argentine soccer legend Diego Maradona were required to obtain and wear them.

Russian authorities are able to track every person’s entry into every game. That might have allowed authorities to locate Rodrigo Vicentini, a fan who had been wanted by authorities in Brazil for two years on charges of robbing a post office.

Vicentini, a 31-year-old Brazilian clad in his national team’s jersey, had just watched his team score two late goals in a tense victory over Costa Rica on June 22 when Russian security officers pounced. They had cross-checked the Interpol wanted list with Fan ID information and arrested him as he left the stadium. He is awaiting extradition to Brazil.

Russian authorities said that they have conducted background checks on all recipients of Fan IDs, liaising with counterparts around the world in what they said was an effort to prevent terrorists or known hooligans from entering the country or any of the World Cup’s stadiums.

“The Fan ID is to provide full security, full comfort at the stadium for those who are there for football reasons, not any other reasons,” said Alexey Sorokin, chief executive of the local organizing committee.

He said Russian authorities were bound by what he called strict rules relating to the data that are embedded in the government’s contracts with FIFA.

Background checks and badges for fans coming to Russia are “quite understandable,” said Chris Eaton, who was responsible for FIFA’s security plan at the 2010 World Cup in South Africa. “No one denies the threat Russia faces from domestic or international terrorist groups.”

Still, privacy advocates have qualms about the harvesting of so much personal data.

“It’s part of a surveillance economy where you are offered something that sounds enticing, like going to a sporting event without hassle and some freebies, in exchange for valuable personal information,” said Timothy Edgar, a cybersecurity expert who teaches at Brown University.

“Russia should destroy the information as soon as the tournament is over,” Edgar said. “Once the need for the data has gone away, they should do that, because potentially it could be subject to leaking or loss.”

Fan IDs could be here to stay. Officials from Qatar, which will host the 2022 World Cup, have studied the program this month as part of their preparations, according to Colin Smith, FIFA’s competitions director. The organizers of the 2026 World Cup in North America, which will require cross-border movement of fans between the United States, Mexico and Canada, confirmed that they are considering a similar program.

But already the Fan ID has become essential equipment for fans. And the mere threat of the revocation of the privileges it confers — chiefly, the ability to attend matches — may be conditioning fan behavior.

Mexico’s soccer federation, under threat of fines or worse from FIFA over fans’ use of a homophobic chant, issued a warning to “avoid getting your Fan ID taken away from you” in order to tamp down on the slur.

After the warning, the chant stopped (Mexico was eliminated by Brazil on Monday).

News reports have said some fans from Latin American countries who tricked Russian women into joining vulgar chants have been identified through their Fan IDs.

Sorokin said local law enforcement agencies have the final say in determining whether to revoke Fan IDs.

But strolling along Teverskaya Street, one of the main thoroughfares leading to Red Square, any such concerns were the last thing on the mind of soccer fans like Pierre Louvat. A 71-year-old from Reunion, a French territory in the Indian Ocean, Louvat said he could not be happier with his Fan ID.

Speaking over his son, who also could not contain his joy with his own World Cup credential, Louvat exclaimed, “C’est magnifique.”

“You can do everything with this,” he said in French. “Plus, it’s going to be a souvenir of the World Cup.”

© 2018 The New York Times Company