The Chinese government is suspected to be behind the hack of the hotel owner Marriott International Inc., that included the theft of data relating to over 500 million customers worldwide.

Reuters reported Wednesday that unnamed security experts examining the hack have found hacking tools, techniques and procedures previously used in attacks attributed to Chinese hackers. The report also noted that the campaign may have been designed to collect information for use in Beijing’s espionage efforts, not for financial gain.

One expert did caution that it’s possible somebody else was behind the hack, because other parties had access to the same hacking tools, some of which have previously been posted online.

China strongly denied the report. “Beijing opposes any groundless allegations and calls for evidence to be provided in relation to the Chinese government’s alleged involvement in the massive data breach at the Marriott International hotel group,” a spokesperson from the Chinese Foreign Ministry said.

Pointing toward an espionage campaign, Scott Scheferman, senior director of global services at Cylance Inc., told SiliconANGLE that the most surprising aspect of this breach is not the size but that the intruders were in the Starwood network since 2014, well before the acquisition by Marriott in 2016. “For almost five years, the intruders were able to explore and exfiltrate information from the network,” he noted.

Marriott acquired Starwood Hotels & Resorts Worldwide Inc. in 2016 for $13.6 billion. The owner of brands that include Sheraton, Westin, W Hotels, St. Regis, Aloft, Le Meridien, Tribute, Four Points and Luxury Collection seemingly obtained its already hacked computer network as part of the deal.

The data stolen in the hack, which was first detected Sept. 8, included names, passport numbers, addresses, phone numbers, birth dates and email addresses. A small percentage of records stolen are also said to have included scrambled payment card data.

Photo: Marriott