Sources involved in the investigation of the Marriott/Starwood data breach have revealed that Chinese hackers are believed to be behind the incident. Marriott International announced at the end of November that 500 million customer records had been affected by the hacking activity, which apparently had been ongoing since 2014. Information was taken from the Starwood guest reservation database.
https://www.notebookcheck.net/Chinese-hackers-believed-to-be-behind-massive-Marriott-data-breach.376796.0.html