U.S. security think tank Strategic Forecasting Inc (Stratfor) said its website had been hacked and that some of the names of corporate subscribers had been made public.
Stratfor said the breach came from an unauthorized party, while activist hacker group Anonymous claimed responsibility.
"As a result of this incident the operation of Stratfor's servers and email have been suspended," the Austin-based company said in an email on Sunday.
Hackers claiming to be the group Anonymous said they had obtained around 4,000 credit card details, passwords and home addresses on Stratfor's private client list, which was posted on information-sharing website Pastebin.
Anonymous, reported to be a loose-knit group of hackers, became famous for attacking the companies and institutions that oppose WikiLeaks and its founder Julian Assange.
Anonymous has also been linked to attacks on the websites of the PlayStation store, the Church of Scientology and governments around the globe that it considered oppressive.
Stratfor, which describes itself as a provider of strategic intelligence for business, economic, security and geopolitical affairs, said it was "working closely with law enforcement in their investigation and will assist them with the identification of the individual(s) who are responsible".
(Reporting By Jerry Norton, Jim Finkle and Nicola Leske; Editing by Dale Hudson)