Beginning in 2014 or earlier, and continuing through November 2018, hackers exploited vulnerabilities in Starwood's network to access the guest reservation system and steal customer data. Marriott discovered the breach on September 8, 2018 but failed to publicly disclose it until nearly three months later, on November 30, 2018, when it admitted that there had been unauthorized access to the Starwood guest reservation database. This database contained personal customer information, including names, mailing addresses, phone numbers, email addresses, passport numbers, Starwood Preferred Guest account information, date of birth, gender, arrival and departure information, reservation dates, and communication preferences. For some customers, the information also included payment card numbers and payment card expiration dates.