Marriott International hotel grouprevealed it suffered a data breach affecting 500000 of customers, making it one of the largest data breaches reported. Marriott learned in September 2018 that unauthorized access to the network of its Starwood's division has been happening since 2014. In November 2018, Marriott discovered that an unauthorized party had copied and encrypted information. For approximately 327 million of guests, the information includes some combination of name, mailing address, phone number, email address, and passport number. For some, the information also includes payment card numbers encrypted using Advanced Encryption Standard encryption (AES-128) and payment card expiration dates. For the remaining guests, the information was limited to name and sometimes other data such as mailing address, email address, or other information. Marriott started notifying affected guests and as well as law enforcement as of 30 November.