Hilton hotels hit by cyber attack

Hilton did not reveal the extent of the breach, but warned anyone who used credit cards at Hilton Worldwide hotels between November 18 and December 5 of last year or April 21 and July 27 of this year to watch for irregular activity in their accounts.

Information swiped by malicious code that infected systems included credit card holders' names along with card numbers, security codes and expiration dates, Hilton global brands executive vice president Jim Holthouser said in an online post.

The hackers did not get people's addresses or personal identification numbers, according to Holthouser.

Hilton said that it is investigating the breach with the help of third-party forensics experts, law enforcement and payment card companies.

The announcement came just four days after Starwood Hotels, which operates the Sheraton and Westin chains, said that hackers had infected payment systems in some of its establishments, potentially leaking customer credit card data.

The hack occurred at A "limited number" of its hotels in North America, according to Starwood, whose other well-known chains include St Regis and W Hotels.

Starwood said that an investigation by forensic experts concluded that malware was detected in some restaurants, gift shops and other points of sale systems at hotels.