Private investigators involved in a probe into the breach discovered hacking tools, techniques and procedures that were used in earlier cyberattacks that have been linked to Chinese hackers, according to the publication which cited anonymous sources.
These clues suggest Chinese hackers could have orchestrated a campaign with the intention of harvesting data for Beijing's espionage efforts, said the unnamed sources. They also noted that someone else could also have launched the attack because some of the same hacking tools used in the attack were previously made accessible online.
Investigators believe there may have been more than one hacking group inside the guest reservation network for Marriot's Starwood division at the same time. This could make it harder to identify the culprit, as one of the sources noted. It's been four years since the hack was launched in 2014.
The data breach at Marriott, which puts personal information such as credit numbers, names, mailing addresses, phone numbers, email address, passport numbers and other sensitive data at risk, is one of many that have come to light in recent days.
Other breaches include the Cathay Pacific hack, which affected 9.4 million people, and one at Facebook that put the data of 50 million users at risk. Concerned lawmakers on Capitol Hill urged Congress to pass data privacy and security protections to safeguard sensitive consumer information just hours after Marriott announced the data breach on Friday.
This article originally appeared on CBSNews.com partner site CNET.