A former LulzSec member has pleaded not guilty to federal charges that he hacked into the servers of global intelligence company Stratfor and stole credit card data and personal details of 860,000 of its clients.

Jeremy Hammond entered the plea on Monday during a brief hearing in US District Court in Manhattan, the Associated Press reported. He's been held in federal custody since an initial court appearance in Chicago in early March, when federal prosecutors named him as a lieutenant of LulzSec ringleader Hector Xavier "Sabu" Monsegur. There was no request for Hammond to be released on bail during Monday's hearing, according to the AP report.

In an indictment filed in May, federal authorities said Hammond stole data for about 60,000 credit cards from Stratfor servers, as well as e-mail and other information for about 860,000 of the service's clients. Hammond, who allegedly used online handles including "sup-g" and "Anarchaos," was also accused of penetrating servers belonging to the Arizona Department of Public Safety and stealing law enforcement documents. He faces charges of conspiracy to commit computer hacking and related offenses associated with the attacks.

Although LulzSec members took great pains to distance themselves from their real-world identities, Hammond was in part identified by statements he made in online chats. In one, he revealed that a friend had been arrested during protests last August in St. Louis. In another, he said he had been arrested in New York City during the Republican National Convention in 2004. He also mentioned serving time in federal prison. FBI investigators used the details to narrow this list of suspects.

Hammond's next court appearance is scheduled for July 23, the AP said.