The US has charged five members of the international hacking group - 'Anonymous' for carrying out cyber attacks against top American companies and stealing classified information on over one million people.

A sixth hacker has pleaded guilty to a 12-count information charging him with computer hacking conspiracies and other crimes.

The hackers are aligned with the group Anonymous, a loose confederation of computer hackers and with other offshoot groups including 'Internet Feds', 'LulzSec' and 'AntiSec'.

Those charged with the computer hacking conspiracy are Ryan Ackroyd, Jake Davis, Darren Martyn, Jeremy Hammond and Donncha O'Cearrbhail.

Hector Xavier Monsegur, also known as 'Sabu', pleaded guilty last year to the computer hacking conspiracies.

According to the indictment unsealed today in Manhattan federal court, the men targeted networks of companies like Fox Broadcasting, Sony Pictures Entertainment and Public Broadcasting Service (PBS).

Hammond, who identified himself as a member of AntiSec, was arrested in Chicago and charged with crimes relating to the December 2011 hack of Strategic Forecasting (Stratfor), a global intelligence firm in Texas, which may have affected approximately 860,000 victims.

He also stole credit card information of approximately 60,000 users and used some of the stolen data to make unauthorised charges exceeding USD 700,000.

He then publicly disclosed some of the confidential information he had stolen.

Monsegur and other members of Anonymous were responsible for a number of cyber attacks between December 2010 and June 2011 against the websites of Visa, MasterCard and PayPal, as retaliation for the refusal of these companies to process donations to website WikiLeaks.

Between December 2010 and May 2011, members of Internet Feds engaged in a series of cyber attacks that included breaking into computer systems, stealing confidential information, publicly disclosing stolen confidential information, hijacking victims' e-mail and Twitter accounts and defacing victims' internet websites.

Specifically, Ackroyd, Davis, Martyn, O?Cearrbhail and Monsegur stole confidential data pertaining to 80,000 user accounts and hacked the computer systems of Fox Broadcasting from which they stole data relating to more than 70,000 potential contestants on Fox's show 'X-Factor'.