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Sony Music Entertainment spokeswoman Liz Young said the company noticed a breach of its systems in May, "and immediately took steps to secure the site and notify authorities. As a result, the two suspects were arrested."
She said no customer data were compromised in the attack on the company's internal music-sharing system.
Sony would not confirm how much music was stolen or what artists were involved. But a person familiar with the situation, who was not authorized to speak publicly, said Monday that the suspects were Jackson fans and had taken his music, including unreleased material.
The year after the King of Pop's 2009 death, Sony signed a 7-year deal with his estate, worth up to $250 million, to sell his unreleased recordings.
Britain's Serious Organized Crime Agency said two suspects were arrested in May and charged in September with computer misuse and copyright offenses.
James Marks, 26, and James McCormick, 25, appeared at Leicester Crown Court in central England on Friday and pleaded not guilty. They were freed on bail and are due to stand trial in January.
The case is not believed to be linked to Anonymous or Lulz Security - loose-knit hackers' collectives, broadly sympathetic to the WikiLeaks' secret-spilling site - who have targeted government and corporate websites around the world.
Last year, hackers compromised credit card data, email addresses and other personal information from millions of users of Sony's PlayStation and Sony Online Entertainment networks. At the time, Lulz Security claimed responsibility for the hack.
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