The Chicago-based hacker who once threatened to burn down the White House and took credit for an devastating computer attack on intelligence company Stratfor made his first appearance in a New York federal courtroom, after his March 5 arrest.

Jeremy Hammond, a 27-year-old with close ties to hacker group LulzSec, wore a bright orange T-shirt under prison-issue navy blue garb and glanced furtively around the magistrate’s courtroom as he was led in, his face pale and his long hair unkempt. Hammond faces federal charges of conspiracy to commit computer hacking, computer hacking and access device fraud. Authorities say the ex-con is known for exhorting fellow hackers to violent acts and once mocked the 9/11 attacks.

But while his computer persona, which emerged under online names such as “Anarchaos” and “crediblethreat” and “tylerknowsthis,” showcased virulent anti-government beliefs, Hammond was respectful in court before the magistrate, who frequently handles early proceedings before cases go to district judges.

“Yes, your honor,” Hammond told Magistrate Judge James Francis when asked if a financial affidavit submitted on his behalf was accurate. Francis approved Hammond's petition to have attorney Liz Fink represent him.

Hammond chuckled when Fink asked a prosecutor if today was the Ides of March and said, “Et tu Brutus?” a possible reference to the betrayal Hammond might have felt at learning he and other hackers were undone by LulzSec leader-turned government informant Hector Xavier Monsegur, known online as “Sabu.”

Monsegur’s FBI handler was present but declined to comment after the proceeding.

Hammond faces up to 10 years in prison and $250,000 in fines on the hacking-related charges and 15 years and $250,000 on the fraud charge if convicted. Francis ordered him held, though Fink said she expects to apply for bond before the next court date, which is April 2.

“This is going to be fun,” Fink said afterward of the case, noting the hacker has a large group of supporters in New York.

Hammond took credit for the massive attack on the global intelligence company Stratfor and even embraced being branded a “terrorist” in a speech at a 2004 hacker convention caught on video. Chat logs first reported by FoxNews.com captured the dark and disturbing views of Hammond, whose mother said he has an IQ of 168 and called him a “genius without wisdom,” in a Chicago Tribune interview.

In the discussions with an unknown audience, Hammond hailed the 2007 book “How Nonviolence Protects the State,” by self-proclaimed anarchist Peter Gelderloos, praising it for encouraging violence and sabotage.

“I didn't start the conversation about burning the white house (sic), but I'll finish it,” vowed Hammond in one undated post.

In another post, Hammond calls for “organized, coordinated attacks against targets who are more directly responsible for our miserable conditions,” and proposes “a toast to the rich! with our choice of cocktail.”

Perhaps most disturbing is this chilling dialogue about 9/11:

“So what's the best way to celebrate 9/11? A jenga tournament!” Hammond posted. “We played a big 9/11 show on saturday, we had a pinata of the world trade towers … it was filled with candy and miniature plastic army men.”

“This guy is not some harmless kid living in his parents’ basement,” a law enforcement source said of Hammond. “He’s got a history and potential for violence.”

In 2005, Hammond formed a group he dubbed the “Internet Liberation Front.” He hacked into a conservative website and stole 5,000 credit card numbers which he intended to use to make donations to liberal causes, according to authorities. Although he was caught before he could carry out the plan, which prompted comparisons to Robin Hood, he served two years in prison.

Hammond was arrested again in 2010 for allegedly throwing a banner into a fire at a protest against the Olympics coming to Chicago. He was given 18 months on probation.

Authorities believe Hammond was the main player in the Stratfor hack last December, in which 5 million emails were stolen and handed over to WikiLeaks. According to the federal complaint against Hammond, the attack was designed to bankrupt Stratfor, a Texas-based company that works with intelligence agencies around the world.