NEW BRUNSWICK Rutgers University continued to work Monday afternoon to bring its computer systems back to full functionality after a distributed denial-of-service attack Friday afternoon brought down the university's email, wireless Internet access, homepage, and Sakai online course management system.

The FBI was assisting in the investigation, the university said.

A distributed denial-of-service attack involves using multiple computers - often a "botnet" of tens of thousands of computers infected by a virus without users' knowledge - to make requests of a server, overwhelming it.

Rutgers' universitywide attack began Friday afternoon, the university said.

"The Rutgers Office of Information Technology (OIT) has been working around the clock to resolve service interruptions," the school said in a message sent to students, faculty, and staff.

That work continued Monday evening - "They're still working to resolve the issue," university spokesman E.J. Miranda said - and the Sakai system remained unavailable.

That system, accessed through a web browser, gives students access to course content. It is also used as a collaboration tool for research and group projects.

It is not used for class registration or transcripts, said Miranda, who affirmed what the university had said in its earlier message:

"OIT has not detected any instances of a breach of confidential information and continues to monitor closely for any such occurrence," the university message said.

After Friday's attack, university email "was affected intermittently," Miranda said. The main home page but was down for a while, and the "RU Wireless" Internet network was brought down Friday.

WiFi access was restored over the weekend, Miranda said.

Citing the ongoing investigation, Miranda declined to comment on reports of an individual claiming responsibility for the attack.

- Jonathan Lai