The University of California, Los Angeles alerted about 800,000 current and former students, faculty, and staff on Dec. 12 that their names and certain personal information were exposed after a hacker circumvented computer security and broke into a campus database.

Only a small percentage--"far less than 5 percent"--of the records in the database were actually accessed, UCLA spokesman Jim Davis told the Associated Press.

Still, it was one of the largest such computer security breaches ever involving a U.S. school.

The attacks on the database began in October 2005 and ended Nov. 21 of this year, when computer security technicians noticed suspicious database queries, according to a statement posted on a school web site set up to answer questions about the theft.

Davis said the hacker used a program designed to exploit an undetected software flaw to bypass computer security systems and get into the restricted database, which has information on current and former students, faculty, and staff, as well as some student applicants and parents of students or applicants who applied for financial aid.

"In spite of our diligence, a sophisticated hacker found and exploited a subtle vulnerability in one of hundreds of applications," Davis said in a statement.

Fortunately, many of the records in the database do not link names and Social Security numbers, however--the two pieces of information the hacker was after, Davis said.

The university's investigation so far shows only that the hacker sought and obtained some of the Social Security numbers. But out of caution, the school said, it was contacting everyone listed in the database.

Acting Chancellor Norman Abrams said in a letter posted on the site that while the database includes Social Security numbers, home addresses, and birth dates, there was no evidence that any data have been misused.

The letter suggests, however, that recipients contact credit reporting agencies and take steps to minimize the risk of potential identity theft. The database does not include driver's license numbers or credit card or banking information.

"We have a responsibility to safeguard personal information, an obligation that we take very seriously," Abrams wrote. "I deeply regret any concern or inconvenience this incident may cause you."

The breach is among the latest involving universities, financial institutions, private companies, and government agencies. Earlier this year, a stolen Veterans Affairs laptop contained information on 26.5 million veterans, and a hacker into the Nebraska child-support computer system might have gotten data on 300,000 people and 9,000 employers.

Computer security experts said the UCLA breach, in the sheer number of people affected, appeared to be among the largest at an American college or university.

"To my knowledge, it's absolutely one of the largest," Rodney Petersen, security task force coordinator for Educause, a nonprofit higher education association, told the Los Angeles Times.