Hackers stole information on as many as 500 million guests of the Marriott hotel empire over four years, obtaining credit card and passport numbers and other personal data, the company said Friday as it acknowledged one of the largest security breaches in history.
The full scope of the failure was not immediately clear. Marriott was trying to determine if the records included duplicates, such as a single person staying multiple times.
It was also unclear what hackers could do with the credit card information. Though it was stored in encrypted form, it was possible that hackers also obtained the two components needed to descramble the numbers, the company said.
The crisis quickly emerged as one of the largest data breaches on record. By comparison, last year's Equifax hack affected more than 145 million people. A Target breach in 2013 affected more than 41 million payment card accounts and exposed contact information for more than 60 million customers.
The New York attorney general opened an investigation.
Security analysts were alarmed to learn that the breach began in 2014. While such failures often span months, four years is extreme, said Yonatan Striem-Amit, chief technology officer of Cybereason.
The affected hotel brands were operated by Starwood before it was acquired by Marriott in 2016. They include W Hotels, St. Regis, Sheraton, Westin, Element, Aloft, The Luxury Collection, Le Méridien and Four Points. Starwood-branded timeshare properties were also included.
None of the Marriott-branded chains were threatened.
For as many as two-thirds of those affected, the exposed data could include mailing addresses, phone numbers, email addresses and passport numbers. Also included might be dates of birth, gender, reservation dates, arrival and departure times and Starwood Preferred Guest account information.
"We fell short of what our guests deserve and what we expect of ourselves," CEO Arne Sorenson said in a statement. "We are doing everything we can to support our guests, and using lessons learned to be better moving forward."
Marriott set up a website and call center for customers who believe they are at risk.
The stolen information could be used by criminals to create fraudulent bank accounts.
It isn't common for passport numbers to be part of a hack, but it is not unheard of. While the credit card industry can cancel accounts and issue new cards within days, it is a much more difficult process, often steeped in government bureaucracy, to get a new passport.
Email notifications for those who may have been affected begin rolling out Friday.
While the first impulse for those potentially affected by the breach could be to check credit cards, security experts say other information in the database could be more damaging.
The names, addresses, passport numbers and other personal information "is of greater concern than the payment info, which was encrypted," analyst Ted Rossman of CreditCards.com said, citing the risk of fraudulent accounts.