Hacker group Anonymous hits security firm

The hacker's group Anonymous has admitted that it raided the computers of U.S.-based security think tank Stratfor and stole thousands of credit-card numbers and other personal information from its clients, AP reports.

Clients confirmed the attack, saying they had already noticed unauthorized transactions on their credit cards, including to charities.

Austin-based Stratfor's customers include Apple, the Air Force, and the Miami Police Department. Anonymous says it will release more data this week, AP said.

"Not so private and secret anymore?" Anonymous posted on Twitter. "Worry not, fellow pirates and robin hoods," it added. "These are just the 'A's."

The group said that it was able to get the credit card details in part because Stratfor didn't encrypt them - if true, that would be a big embarrassment for a security-related company.

Fred Burton, Stratfor's vice president of intelligence, said that the company has protections to prevent such attacks and that the police had been notified. "But I think the hackers live in this kind of world where once they fixate on you or try to attack you, it's extraordinarily difficult to defend against," Burton told AP.

Anonymous has also claimed to have attacked Visa, MasterCard, PayPal, and the Church of Scientology.