Journalists are silhouetted during Nintendo Co Ltd's news conference in Chiba, east of Tokyo, in this October 10, 2007 file photo. Nintendo's US-based servers were attacked several weeks ago but no consumer data was stolen, the company said on June 5, 2011. Nintendo is the latest company to be targeted by cyber criminals in a hacking attack. In April, hackers broke into Sony Corp's servers and exposed the personal information of more than 100 million of its customers. Picture taken October 10, 2007. [Photo/Agencies]

Hackers calling themselves Lulz Security said on Monday that they had broken into Sony Corp computer systems again, and posted the results on the Internet.

The group, which has claimed credit for a prior attack on Sony's systems, posted what appeared to be Sony BMG network maps from a New York city office and what they said was 54 megabytes of Sony developer source code.

"We're not commenting on this issue," said Sony Music spokeswoman Liz Young.

Last week, the group said it had broken into Sony's computer network and accessed information on more than 1 million customers to show the vulnerability of the company's systems. In that attack, the group of hackers, who have managed to keep themselves anonymous, published names, birth dates, street addresses, email addresses, phone numbers and passwords of people who had entered contests promoted by Sony.

On April 26, Sony warned that hackers had stolen personal information from 77 million user accounts of its video game online network. On April 19, Sony pulled the plug on its PlayStation Network after discovering the breach.

On May 2, Sony revealed that hackers had stolen data another 25 million users of its PC games system.

Last week, Lulz Security claimed credit for an attack on an Atlanta office of InfraGard, an outreach center used by the Federal Bureau of Investigation to liaise with private business.

InfraGard and the FBI did not respond to requests for comment.

Lulz Security has claimed responsibility for defacing the US Public Broadcasting Service network websites, and for posting on Monday data from PBS servers to protest a "Front Line" documentary about WikiLeaks.

It has also claimed credit for breaking into a Fox.com website and publishing data about contestants for the upcoming Fox TV talent show, "X Factor."

Defense contractor Lockheed Martin and Google Inc have also been hacked recently.

Nobody has claimed responsibility for the attacks that Sony disclosed in April and May.