"I'm not the same person as four years ago," said Tuesday Hector Xavier Monsegur, who was arrested in June 2011 for stealing credit card information and sentenced to 20 years but, thanks to his "extraordinary cooperation" with the FBI, now walks free.
The 30-year-old computer hacker helped the government disrupt hundreds of cyberattacks on Congress, NASA and other sensitive targets, as well as cripple the hacktivist crew known as Anonymous.
He got a hero's welcome Tuesday at his sentencing in federal court, where prosecutors hugged him after he was spared more prison time.
U.S. District Chief Judge Loretta A. Preska credited Monsegur's "extraordinary cooperation" before saying he won't serve more than the seven months he spent in prison two years ago. Federal sentencing guidelines had called for more than 20 years in prison.
"It was truly extraordinary," she said of his cooperation, noting he worked around-the-clock for months, disrupting or preventing at least 300 computer hacks over the last three years. "We don't often hear of this."
Prosecutors said he helped disrupt or prevent hacks against divisions of the U.S. government including the armed forces, Congress, courts and NASA; international intergovernmental organizations; and several private companies, including a television network, a security firm, a video game maker and an electronics conglomerate.
Prosecutors said he prevented millions of dollars in losses and also pointed out vulnerabilities in infrastructure, including at a U.S. water utility and at a foreign energy company.
In one instance, Monsegur saved the government substantial time and resources by quickly establishing that a claim by Anonymous that it had hacked the U.S. electrical grid was a hoax, prosecutors said.
According to court papers, Monsegur first began hacking in 1999, breaking into thousands of computers over the next four years before trying to grow a legitimate computer security firm from 2004 to 2006.
In 2006, he began to hack into computers for personal gain, stealing credit card information, prosecutors said.
In a 2011 interview with the online magazine New Scientist, Monsegur said he joined forces with Anonymous because he was upset over the arrest of WikiLeaks founder Julian Assange.
Starting in early 2011 and using the alias Sabu, Monsegur led an Anonymous splinter group called Lulz Security, or LulzSec, which hacked the computer systems of Fox television, Nintendo, PayPal and other businesses, stole private information and bragged about its exploits online.
The group was loosely affiliated with Jeremy Hammond, the FBI's most wanted cybercriminal, whose stated objective was to cause mayhem with the attacks, prosecutors said.
After his arrest, Monsegur immediately cooperated, giving the FBI a tutorial on the inner workings and participants of LulzSec and Anonymous, prosecutors said.
Now, attorney Philip Weinstein said his client seeks work and would not rule out a government job.
"He's taught the government things they don't know," he said.
Based on reporting by The Associated Press.