For the third time in less than two years, hackers breached UCSD’s computer systems, this time holding up a number of online services in the social sciences division, including Web mail servers, as students prepared for midterm exams.

Students and professors found themselves unable to access class Web sites after the division shut down some online services because of a hacking into the system. No personal information was accessed, programmer analyst Thanh Nguyen said.

Records show that the hacker had access only to services a regular Web site user would see and was limited in the damage he or she could have caused.

The hacker triggered red flags by sending a large number of requests from a Web account to contact other servers, which changed patterns in incoming and outgoing requests. This alerted the social sciences computing facility that something was not running smoothly, which led to the temporary shutdown of the system by the department.

The incident was less serious than a fall 2004 hacking in which students’ Social Security numbers and bank account information were exposed. Because the social science division does not keep private information, the hacker did not have access to that kind of data, Nguyen said. People who had opted to forward their campus e-mail to outside accounts were blocked from using the system during the shutdown, but anyone who used the UCSD Web mail service should have received messages as usual, said Bunnie Jacquay, the administrative manager of the social science computing facility.

Nevertheless, both students and faculty members missed appointments and some meetings did not take place because of miscommunication, communications professor Michael Cole said. Faculty had to deal with an overload of students at office hours requesting responses to questions that had been asked through the department’s Web site, he said.

Cole said the shift toward modern media, especially Internet-based communication, widens the gap between people’s knowledge and the use of simpler — and now less frequent — communication methods.

Measures are being taken to improve the security system and the safety of users, Nguyen said. The division is working with campus security and other servers as well.

“We are increasing our avenues so that not everything feeds through one channel,” Jacquay said.

Because some classes no longer hand out paper copies of syllabi and use class Web sites instead, a system breakdown can often cause a break in the learning process, John Muir College junior Stacey Grandy said.