Staff at the Sonoma State University are busy notifying 61,000 students who attended or applied to the university between 1995 and 2002.
According to the university, the hacker targeted several staff workstations.
"After the illegal access was confirmed, Information Technology took immediate action to secure the computers," said the university in a statement on its website. "There is no evidence that personal information was retrieved."
The university is now investigating the breach.
The news arrives days after hackers hit University of Colorado for the second time in two weeks. The hacker gained access to the university identity and access cards, known as Buff OneCards, which contain personal information including Social security numbers.
Some reports suggest the previous incident was from a server in France. The university said there is as yet no indication that the incidents are connected and that a programme to replace the cards is being implemented.
It has been high drama all year at U.S. universities. In July