A breach of customer data on Sony Online Entertainment servers, may be the work of hackers acting under the name of “Anonymous”, according to Sony.

Sony sent a letter to the U.S. House of Representatives on Wednesday, indicating that they have found a file left behind by the hackers on their systems. The text file left behind carried the name “Anonymous” and the words “We Are Legion”.

The Anonymous name refers to a loosely-organized group of protesters who stage real-world protests coupled with “hactivisim”, an activity including hacking and denial-of-service attacks against large companies. Anonymous typically acts under the banner of free speech or other freedoms, with most attacks staged in response to a specific action.

Anonymous did carry out a number of denial of service attacks against Sony in response to Sony’s lawsuits agains George Hotz. Hotz and others were sued by Sony for jailbreaking the Sony PlayStation 3, hacking its security systems so that unauthorized software could be run on the system. During investigations into the suit, Sony was also given access to IP addresses of people who visited Hotz’s blog, where information about hacking the PS3 was published. The IP addresses were meant to provide information about what jurisdiction would hear the case.

Sony said that investigating the known denial-of-service attack, it found evidence that some hackers had broken into the PlayStation Network servers, compromising 77 million PSN accounts. This discovery was announced on April 26. On Monday May 2, Sony announced that Sony Online Entertainment servers were also the victim of a break-in, and it is here that they found the Anonymous file.

Hackers under the Anonymous name took credit for the denial-of-service attacks in response to the lawsuit against Hotz and the release of IP addresses to Sony. However, Anonymous as a group has not claimed responsibility for the server break-ins.

The security breach reportedly compromised personal data for 24.6 million PSN members, including credit card or banking information for about 20,000 members.

Sony says it will begin to restore services this week, and will offer PSN subscribers a free month subscription of its PlayStation Plus service, including a variety of free downloads.

Sony has announced that over 21 million PlayStation 3 consoles have now been sold worldwide, with 17 million accounts registered on the online PlayStation Network.

The announcement comes alongside news that Sony plans to take on Latin America by releasing its PS3, PS2 and PSP systems there.

The company’s phased approach involves eventual expansion to thirteen countries in the area, beginning with Argentina, Chile, Columbia and Peru in the first phase.  Sony also plans to set up a localized PlayStation Network in the area.

Ian Jackson, VP of sales at SCEA, has high hopes for the region.  “Long-term it has a very good opportunity to be bigger for SCEA than the Canadian market was,” he says.