A prominent hacker set to be sentenced in federal court this week for breaking into numerous computer systems worldwide has provided a trove of information to the authorities, allowing them to disrupt at least 300 cyberattacks on targets that included the U.S. military, Congress, the federal courts, NASA and private companies, according to a newly filed government court document.
The hacker, Hector Xavier Monsegur, also helped the authorities dismantle a particularly aggressive cell of the hacking collective Anonymous, leading to the arrest of eight of its members in Europe and the United States, including Jeremy Hammond, who the FBI said was its top "cybercriminal target," the document said. Hammond is serving a 10-year prison term.
The court document was prepared by prosecutors who are asking a judge, Loretta A. Preska, for leniency for Mr. Monsegur because of his "extraordinary cooperation." He is set to be sentenced Tuesday in U.S. District Court on hacking conspiracy and other charges that could result in a long prison term.
It has been known since 2012 that Mr. Monsegur, who was arrested in 2011, was acting as a government mole in the shadowy world of computer hacking, but the memorandum submitted to Judge Preska late Friday reveals for the first time the extent of his assistance and what the government perceives of its value. It also offers the government's first explanation of Mr. Monsegur's involvement in a series of coordinated attacks on foreign websites in early 2012, though his precise role is in dispute.
The whereabouts of Mr. Monsegur have been shrouded in mystery. Since his cooperation with the authorities became known, he has been vilified online by supporters of Anonymous, of which he was a member. The memo said the government became so concerned about his safety that it relocated him and some family members. "Monsegur repeatedly was approached on the street and threatened or menaced about his cooperation once it became publicly known," said the memo, which was filed by the office of Preet Bharara, U.S. attorney in Manhattan.
Born in 1983, Mr. Monsegur moved to the Jacob Riis housing project on the Lower East Side of Manhattan at a young age, where he lived with his grandmother after his father and aunt were arrested for selling heroin. He became involved with hacking groups in the late 1990s, drawn, he has indicated, to the groups' anti-government philosophies.
Mr. Monsegur's role emerged in March 2012 when the authorities announced charges against Hammond and others. A few months later, Mr. Monsegur's bail was revoked after he made "unauthorized online postings," the document said without elaboration. He was jailed for about seven months, then released on bail in December 2012, and has made no further postings, it said.
The memo said that when Mr. Monsegur (who used the Internet alias Sabu) was first approached by FBI agents in June 2011 and questioned about his online activities, he admitted to criminal conduct and immediately agreed to cooperate with law enforcement.
That night, he reviewed his computer files with the agents, and throughout the summer, he daily "provided, in real-time, information" that allowed the government to disrupt attacks and identify "vulnerabilities in significant computer systems," the memo said. "Working sometimes literally around the clock," it added, "at the direction of law enforcement, Monsegur engaged his co-conspirators in online chats that were critical to confirming their identities and whereabouts."
His primary assistance was his cooperation against Anonymous and its splinter groups Internet Feds and LulzSec.