Hyatt Hotels has announced that malicious software has been discovered in close to 250 of its hotels, possibly compromising customers' credit and debit-card numbers, as well as other information. The hotel giant originally announced the malware discovery in December, but for the first time it has now announced the locations that were affected by the attack. The chain also announced that it does not know at this time how many customers were affected.

Management of the corporation says the malware was present between at approximately 100 locations U.S. locations between July and December at payment-processing systems at its restaurants, spas, front desks and other areas. Malware was found at many of its brands, including the Park Hyatt, Hyatt Regency and Andaz in the U.S. and abroad, with close to 150 locations affected in cities including London, Paris and Shanghai.

Hyatt Hotels Corp., a Chicago based company, operates approximately 630 hotels and resorts around the world. For a list of affected Hyatt locations, please go to