This adds to a recent string of attacks on major hotel firms' payment systems
The US Hyatt Hotel chain has said that its payment processing system has been targeted by credit-card stealing malware.
The attack was discovered on November 30th - a spokesperson did not comment on whether the hackers had successfully stolen credit card details.
"Customers should review their payment-card account statements closely and report any unauthorised charges to their card issuer immediately," the group said in a statement.
Hyatt is controlled by the billionaire Pritzker family - it is the fourth major hotel chain to report an attack on its payment system.
Hilton, Starwood and Donald Trump's hotel chain have experienced similar incidents.
The chain is working with FireEye - one of the largest suppliers of online security services for companies.
"We have taken steps to strengthen the security of our systems.
"Customers can feel confident using payment cards at Hyatt hotels worldwide," a Hyatt spokesperson said.