Sony's sad security song isn't finished yet.

Hackers have reportedly broken into the music label's servers and downloaded Michael Jackson's entire 50,000-track catalog, including many songs that have never been released, according to a report in Britain's Sunday Times (behind paywall). Sony purchased the catalog in 2010 from Jackson's estate for $250 million--billed as the biggest recording deal in history.

"Everything Sony purchased from the Michael Jackson estate was compromised," a source told the newspaper. "It caused them to check their systems and they found the breach. There was a degree of sophistication. Sony identified the weakness and plugged the gap."

Two men in the U.K. have been arrested and charged in the crime, according to The Guardian. They have reportedly been released on bail and are scheduled to stand trial in January 2013.

The intrusion, which netted collaborations with the Black Eyed Peas' will.i.am and late Queen front man Freddie Mercury, was discovered weeks after the massive security breach on Sony's PlayStation Network last April. After a mysterious weeklong outage on the service, the company finally informed some 77 million customers that critical personal information, including names, addresses, e-mail addresses, birthdays, usernames, and passwords were obtained illegally obtained by an "unauthorized person."

The entertainment and electronics giant eventually issued an apology and said it would provide its customers with free identity theft protection services. But that breach was followed up a month later with hacks on Sony Music Japan and Sony Ericsson's online store. Last June, the LulzSec hacker group released what it described as 54MB of source code from the Sony Computer Entertainment Developer Network as well as internal network maps of Sony BMG.

There is no word on whether the songs illegally downloaded have made an appearance on the Internet. However, protecting unreleased songs from unauthorized debuts has become a special challenge in recent years.

Four songs from U2's then-unreleased "No Line on the Horizon" appeared on the Internet in 2008 after the Irish rock band's front man Bono was allegedly caught playing the songs a bit too loudly on his stereo at his villa in the south of France.