Stratfor provides political, economic and military analysis to help clients "reduce risk," according to the company. The company's main website is currently down, with a banner saying the "site is currently undergoing maintenance."
Hackers said the goal was to get funds from individuals' accounts to give away as Christmas donations.
Anonymous tweeted a link to encrypted files online with names, phone numbers, emails, addresses and credit card account details. This was only a part of the 200 gigabytes worth of plunder it stole from Stratfor and promised more leaks. It said it was able to get the credit card details in part because Stratfor had not encrypted them.
Responding to the attack, Stratfor has hired an identity theft protection and monitoring service.
The Anonymous group has previously claimed responsibility for attacks on credit card companies Visa and MasterCard, PayPal, as well as other groups in the music industry.
The Anonymous group posted a disclaimer on the Internet saying the group isn't responsible for the action.
"Hackers claiming to be Anonymous have distorted this truth in order to further their hidden agenda, and some Anons have taken the bait," the goup said in an "Emergency Christmas Anonymous Press Release"
"The Stratfor hack is not the work of Anonymous. Stratfor is an open source intelligence agency, publishing daily reports on data collected from the open Internet. Hackers claiming to be Anonymous have distorted this truth in order to further their hidden agenda, and some Anons have taken the bait," the group claimed.
"The leaked client list represents subscribers to a daily publication which is the primary service of Stratfor. Stratfor analysts are widely considered to be extremely unbiased. Anonymous does not attack media sources."
According to Anonymous, Stratfor has been deliberately misrepresented by "these so-called Anons" and portrayed in false light as a company which engages in activity similar to HBGary.
"Sabu and his crew are nothing more than opportunistic attention whores who are possibly agent provocateurs... As a media source, Stratfor's work is protected by the freedom of press, a principle which Anonymous values greatly. This hack is most definitely not the work of Anonymous," the group added.