Hackers attacked the computer network at the Naval War College in Newport, R.I., and the school's network, including its e-mail and Web site, has been down for more than two weeks as investigators work to find the culprits.

The Navy Cyber Defense Operations Command in Norfolk, Va., detected the intrusion around Nov. 16 and took the system offline, spokesman Lt. Cmdr. Doug Gabos said.

Gabos said the network was unclassified and was used by students at the war college.

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The school's Web site is down and military spokesmen would not give an estimate on when it will be back up.

The Naval War College bills itself as the nation's leading center of strategic thought and national security policy development for the Navy.

It has 581 students, including officers from the Army, Air Force, Coast Guard and Marines, as well as civilian and international students.

The Navy's networks are probed thousands of times a day, but intrusions such as this are rare, Gabos said Tuesday. He said it was uncommon for the Navy to take a system completely offline.

Investigators are trying to determine the extent of the intrusion, Gabos said. They will also upgrade the firewalls and other unspecified steps.

"Once that is complete, the network will be restored," Gabos said.

Tim Madden, a spokesman for the military's Joint Task Force-Global Network Operations, would not comment on why the school's network has been down for more than two weeks.

"These things are done on a case-by-case basis, and we do the things that are necessary," he said. "You want to be thorough."

Neither Gabos or Madden would comment on who is suspected of attacking the network.