In federal court Friday Engineering junior Ryan Goldstein pleaded guilty to helping a hacker crash the School of Engineering and Applied Science's server in February 2006.
Goldstein pleaded guilty to aiding and abetting another person to gain unauthorized access to a protected computer, a federal misdemeanor.
Goldstein was arrested last November, after a grand jury indicted him for conspiracy to commit computer fraud, a more severe offense than the charge to which Goldstein pleaded.
Goldstein remains enrolled at the University, according to University spokeswoman Lori Doyle. His sentencing is set for June 3.
Goldstein was one of eight people arrested last fall as part of an international FBI investigation.
He collaborated with Owen Walker, a New Zealand-based hacker known online as AKILL, to carry out attacks by using a fellow Penn student's username and password to access the Penn server.
The 2006 SEAS server crash was caused by an inundation of traffic on the server, and denied access to 4,000 students, faculty and staff.
His plea came just before his trial date, March 10. Goldstein requested a change-of-plea hearing last week.
Sentencing guidelines for the misdemeanor charge Goldstein are based on the estimated $6,000 in proprietary damages prosecutors say he caused.
Goldstein faces "zero to six months" of incarceration, Assistant U.S. Attorney Michael Levy said. Levy did not say which punishment he would ask for at sentencing.
However, Goldstein's lawyer, Ronald Levine, said that Goldstein "is eligible for probation."
If Goldstein had gone to trial on the charge of conspiracy to commit computer fraud, he could have faced up to five years in prison.
The plea also allows Goldstein to avoid a trial in which the potentially embarrassing details of his involvement in an online chat forum leading to his collaboration with Walker would be brought to light.
The indictment states that Goldstein was involved in "online disputes" with other Internet users, and wanted to retaliate against a forum that had banned him.
Goldstein "apologized for his actions" in court, Levine said.
Goldstein did not return phone calls for comment.
