University of Missouri officials said campus computer technicians confirmed a breach of a database last week by a user or users whose Internet accounts were traced to China and Australia.
The hacker accessed personal information of 22,396 University of Missouri-Columbia students or alumni who also worked at one of the system's four campuses in St. Louis, Kansas City, Rolla or Columbia in 2004.
The hacker obtained the information through a Web page used to make queries about the status of trouble reports to the university's computer help desk, which is based in Columbia. The information had been compiled for a report, but the data had not been removed from the computer system.
In January, a hacker obtained the Social Security numbers of 1,220 university researchers, as well as personal passwords of as many as 2,500 people who used an online grant application system.
The university is contacting people affected by the latest breach and providing instructions on how to monitor their credit reports and other financial records for suspicious activity, officials said.