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 that has a long history of closely monitoring its citizens. The Russian authorities said the only purpose of the badges is to improve the security and comfort of fans. The badges, however, do give World Cup organizers and security officials the ability to track the location of fans during the tournament and provide the authorities those fans’ personal information.