Eastern Illinois University officials this week said they are investigating how and why hackers infiltrated the school's admissions server last month, gaining access to the personal information of more than 9,000 former, current, and prospective students.

According to a posting on the university's Web site, someone gained access to the critical server for more than six days in mid-November after the server was infected with the Virut virus.

Eastern Illinois officials said the server then became infected with a number of other viruses that allowed the attackers to have their way with student application data stretching from March 2000 through November of this year.

The breach was discovered during a routine security check of the university's data networks. School officials also said the virus managed to spread to two other administration computers that contained additional personal information from student files and admissions applications.

"EIU officials do not know whether files containing personal information were accessed; however, each individual with information filed on that server has been sent a letter of notification, which includes safety recommendations they can take," the university said on its Web site.

For now, the university is providing the affected students with one year of free credit-monitoring services from Experian.

Eastern Illinois, located in Charleston, Ill., is one of dozens of universities and colleges victimized by hackers in the past year.

In April, University of California at Berkeley officials said hackers infiltrated a health care database containing the personal information of more than 160,00 students dating back to 1999.

In September, the University of North Carolina's radiology department discovered that hackers may have compromised a server containing the personal data of more than 163,000 women participating in a mammography research project.

Similar attacks were reported this year at Chaminade University, Montana State University, the University of Michigan, and the University of Alabama.

Larry Barrett is a senior editor at InternetNews.com. Based in Las Vegas, Larry covers IT management, enterprise software, services and security.