The website of Strategic Forecasting, also known as Stratfor, has been offline for several days following the hacking attack.

"As part of our ongoing investigation, we have also decided to delay the launching of our website until a thorough review and adjustment by outside experts can be completed," Stratfor said in an email.

The firm had earlier disclosed that its website had been hacked and that some information about its corporate subscribers had been made public.

The hacking group known as Antisec has claimed responsibility for the attack and promised to cause "mayhem" by releasing stolen documents.

"An unauthorized party illegally obtained and disclosed personally identifiable information and related credit card data of some of our paying subscribers," Stratfor said in the email.

Stratfor also said in its letter that it would offer identity theft protection and monitoring services to affected subscribers.

(Reporting by Sakthi Prasad in Bangalore; Editing by Ed Lane)

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