NEW YORK — In his Twitter postings, the elite computer hacker known as "Sabu" urged followers to resist the U.S. government and its agents.
But court papers made public Thursday reveal that Hector Xavier Monsegur put up no such fight when FBI agents first knocked on his door on June 7. From almost that first moment, he began talking, naming names and helping investigators pick apart the international community of Internet saboteurs.
He was arrested at 10:15 p.m. By the next day, federal prosecutors had told a judge that Monsegur had given them detailed information on other hackers suspected of breaking into the computer systems at several big corporations.
"Since literally the day he was arrested, the defendant has been cooperating with the government proactively," Assistant U.S. Attorney James Pastore told a judge in New York during a secret court session for Monsegur on Aug. 5. Over the past few months, the prosecutor said: "The defendant has literally worked around the clock with federal agents. He has been staying up sometimes all night engaging in conversations with co-conspirators that are helping the government to build cases against those co-conspirators."
That cooperation resulted in the arrests of five other alleged hackers this week in Ireland, Scotland, England and the U.S., a takedown that stunned fellow Internet saboteurs known for prizing anonymity and a culture of resistance.
Monsegur secretly pleaded guilty in August, but judges had agreed to close public courtrooms and seal all records of his case in order to keep his work with the government from becoming known. Most of those court files have since been unsealed, and documents made available Thursday provided a handful of new details about Monsegur's work.
While software on his computer tracked his online activity and video cameras monitored his home at a New York City public housing project, prosecutors said, Monsegur worked feverishly with the FBI to monitor Internet communications between fellow hackers. In many cases, he helped thwart attacks as they were being planned, prosecutors said in a court filing.
By August, he had worked with the FBI to "patch" 150 vulnerabilities in computer systems being eyed by hackers, or in other cases react quickly to help attack victims mitigate the damage, Pastore said in court.
Prosecutors were concerned from the start with Monsegur's safety if his identity were to be revealed.
"Some of the groups against whom the defendant is cooperating are known to retaliate against people who cooperate with the government in ways ranging from the mundane, for example, ordering hundreds of pizzas to someone's house, to much more serious: calling in hostage situations in part by using family information and having a SWAT team show up at the person's home," Pastore told a judge on Aug. 5.
Prosecutors haven't explained publicly why Monsegur was so willing to work with the government, even as he continued to rail against it in posts online. But court records did note that the 28-year-old was the legal guardian of two young nieces. Neighbors have told The Associated Press that Monsegur was raising the children after his aunt was jailed on drug charges.
Other court papers noted that Monsegur lived on meager means. He had been earning $6,000 per month until losing his job in the spring of 2010, and had since been living off of $400 unemployment checks.
Monsegur has yet to be sentenced for his computer crimes, which included a number of attacks on big corporations, foreign governments and U.S. government agencies.