In a rare misdemeanor hacking case in federal court, a University of Pennsylvania bioengineering student was sentenced yesterday to 90 days in prison and five years' probation for crashing a school server in 2006. But the afternoon hearing was much more: It included tears from the defendant; outrage from the judge over what he called "unfair" justice; and instances of child pornography.

U.S. District Judge Michael Baylson also sentenced Ryan Goldstein, 22, of Ambler, to 90 days in a halfway house followed by 180 days of house arrest and ruled that the defendant, a senior at the university, may serve his sentence during a leave of absence from school or during the summer.

Goldstein, who told the judge he had suffered a "computer addiction" since he was 12, was also fined $30,000 and prohibited from using a computer for five years except for work or school activities.

In February, Goldstein admitted to a single misdemeanor count of aiding and abetting another hacker - Owen Thor Walker, a New Zealand teen known as AKILL - in gaining unauthorized access to a Penn computer server by using a botnet. A botnet is a network of computers - typically home PCs that have been commandeered secretly by hackers - that is programmed by the hackers to launch coordinated, massive "denial of service" attacks on other computers, crashing or immobilizing the targets.

Goldstein and Walker used Penn's computer system as a staging ground for a 50,000-computer attack. The system couldn't handle the flood, which Assistant U.S. Attorney Michael Levy compared to "water coming from a fire hose."

After Goldstein was arrested, he began cooperating with authorities, and his information led to Walker, who installed malicious software on 1.3 million computers worldwide, investigators said. Walker cooperated with authorities in New Zealand and was fined about $11,000 in July, officials said.

Levy, who prosecutes about two computer-hacking cases a year, said that Goldstein's cooperation "in the online hacking world was very useful" and led to at least seven other arrests. The prosecution made no recommendation in court regarding sentencing.

Baylson, however, said he felt some jail time was necessary for Goldstein because the FBI also found more than 1,000 images of child pornography on his computer. Those victims, the judge said, were "unseen and unheard" in court yesterday.

The judge referred to the fact that prosecutors had decided not to charge Goldstein with child pornography in return for his cooperation.

But the judge said he found it tough to sentence another man, Derrick Williams, 32, of Philadelphia, to a heavy prison sentence the same day for the same crime.

"It seems very unfair. . . . I want to note for the record that Mr. Goldstein is white and Mr. Williams is African American and that adds to my discomfort," said Baylson. Both men had roughly 1,000 images of child pornography on their computers, the judge said.

"I just cannot do it," the judge said, and then sentenced both men one right after the other. Baylson sentenced Williams to two years, instead of the eight to 10 years recommended by sentencing guidelines.

Goldstein, who faced up to a year in prison, had been hoping for no prison time. His lawyer, Ronald Levine, had asked for no prison time, saying: "Ryan is filled with constant guilt and remorse."

After the sentence was handed down, Goldstein was initially stoic, but tears streamed down his face as he left the courtroom.

Contact staff writer Jan Hefler

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