STATE COLLEGE — A cybersecurity sweep at Penn State found the Social Security numbers of another 25,000 individuals may have been exposed to a security breach because of infected computers.

But the university said that, as in previous cases, there was no evidence that data had been accessed after the computers were hit by malicious software or so-called "malware." Malware refers to software that can silently install viruses, probe for confidential data or hijack a computer.

Individuals affected by the privacy breaches were notified as required by state law to look out for potential identity theft, Penn State said.

One recent case involved a University Libraries computer breached with malware. The computer contained the Social Security numbers of more than 9,700 people. In another case, the school last week sent letters to more than 15,800 people about a possible breach at an Outreach Market Research and Data computer. The attacks in those cases occurred some time earlier this year, school spokesman Geoff Rushton said Tuesday.

Another 35,000 individuals were notified late last year and earlier this year of potential breaches at the main University Park branch as well as campus sites in Carlisle and Schuylkill Haven.

The university does not know if the 60,000 cases are related, but was working with government agencies on the problem, Rushton said.

Universities across the country are increasingly becoming the targets of stepped-up and more sophisticated malware attacks, Rushton said.