Ticketmaster owner Live Nation confirmed “unauthorised activity” on its database after a group of hackers said they had stolen the personal details of 560 million customers.
ShinyHunters, the group claiming responsibility, says the stolen data includes names, addresses, phone numbers and partial credit card details from Ticketmaster users worldwide.
The hacking group is reportedly demanding a $500,000 (£400,000) ransom payment to prevent the data from being sold to other parties.
In a filing to the US Securities and Exchange Commission, Live Nation said that on 27 May “a criminal threat actor offered what it alleged to be Company user data for sale via the dark web”, and that it was investigating.