Compromised personal information includes full names, email addresses, credit card details and passport numbers of guests that could be used by cybercriminals who are increasingly interested in the movements of influential business professionals and government employees, Symantec said.

The research showed compromises usually occur when a hotel site sends confirmation emails with a link that has direct booking information. The reference code attached to the link could be shared with more than 30 different service providers, including social networks, search engines and advertising and analytics services.