An accused member of the clandestine hacking group LulzSec pleaded not guilty on Monday to charges of taking part in an extensive computer breach of the Sony Pictures Entertainment film studio.

Cody Kretsinger, 23, entered not guilty pleas to one count each of conspiracy and unauthorized impairment of a protected computer during a brief hearing in U.S. District Court in Los Angeles.

U.S. Magistrate Judge Victor Kenton set a December 13 trial date for Kretsinger, who came to court dressed in khaki pants and a blue collared shirt with the sleeves rolled up, and spoke only in response to questions from the judge.

Kenton also ordered that Kretsinger be represented by a court-appointed public defender.

A nine-page federal grand jury indictment unsealed in late September charges Kretsinger with obtaining confidential information from Sony Pictures' computer systems using an SQL injection attack against its website, a technique commonly used by hackers to steal information.

Kretsinger, who went by the moniker recursion, helped post information he and his co-conspirators stole from Sony on LulzSec's website and announced the intrusion via the hacking group's Twitter account, the indictment charges.

LulzSec, an underground group also known as Lulz Security, at the time published the names, birth dates, addresses, e-mails, phone numbers and passwords of thousands of people who had entered contests promoted by Sony.

From a single injection we accessed EVERYTHING, the hacking group said in a statement at the time. Why do you put such faith in a company that allows itself to become open to these simple attacks.

Hackers previously had accessed personal information on 77 million PlayStation Network and Qriocity accounts, the vast majority of which were users in North America and Europe, in what was then the biggest such security breach in history.

Other high-profile firms targeted by cyber attacks included Lockheed Martin and Google Inc.

LulzSec is reputed to be affiliated with the international hackers collective called Anonymous, which has claimed responsibility for cyber attacks on government and private institutions around the world.

Kretsinger faces a maximum sentence of 15 years in prison if convicted. He declined to comment to Reuters after the morning hearing.

(Editing by Dan Whitcomb and Jerry Norton)