The hackers said they took the Stratfor Global Intelligence Service's list of 4,000 clients and had posted the names, along with credit card information, passwords and home addresses, The New York Times reported.
The hackers said they also had details for more than 90,000 credit card accounts.
Stratfor's clients include such corporate, government and non-profit heavyweights as Bank of America, the Defense Department, Doctors Without Borders, Lockheed Martin, Los Alamos National Laboratory and the United Nations.
The hackers said they intend to use the credit card information to send $1 million in donations to charities.
The Times said Stratfor Chief Executive Officer George Friedman confirmed in an e-mail Sunday his organization's site had been hacked and his company was cooperating with law enforcement to find the parties responsible.
"We have reason to believe that the names of our corporate subscribers have been posted on other Web sites," Friedman wrote in the e-mail. "We are diligently investigating the extent to which subscriber information may have been obtained."
In taking responsibility for the Stratfor attack, the hackers said it was just the beginning of a weeklong hacking spree, the newspaper said.
Exploding whale video goes viral on Internet
Couple mistakenly served bag of cash at McDonald's drive-thru