ATHENS, Ga. - University of Georgia officials are scrambling to contact more than 4,000 current, former and prospective residents of the university's graduate family housing complex after an overseas hacker tried to access a server containing Social Security numbers.

The hacker breached the security system sometime between Dec. 29 and Dec. 31, according to a statement UGA released Tuesday.

During that time, a computer with an overseas Internet Protocol address was able to access the personal information, including Social Security numbers, names and addresses, of 540 current graduate students living in graduate family housing and 3,710 former students and applicants.

University officials know what country the hacker was operating in but would not comment on that part of the investigation, UGA spokesman Tom Jackson said.

Workers took the server off line as soon they discovered the problem.

There was no evidence that the hacker used or even recorded the information, according to Stan Gatewood, UGA's chief information security officer.

"It seemed to be one of those things where the door was opened, but no one walked in," said Mr. Jackson. "But still everyone needs to be notified."

Locating and notifying all of the affected people could be prove difficult because many are former students from outside the United States, Mr. Jackson said.

In February a hacker was able to access personal information, including some medical information, on 3,500 current and former students from a server at the UGA Disability Resource Center.

"They've established a campus-wide protocol concerning patches and firewalls and what types of data can be held at what levels of accessibility," Mr. Jackson said. "But even with everything in place, it's hard to stop a determined criminal from breaking through."