The Naval War College bills itself as the nation's leading center of strategic thought and national security policy development for the U.S. Navy. It has 581 students, including officers from the Army, Air Force, Coast Guard and Marines, as well as civilian and international students.

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

Investigators are looking for "forensic evidence" to determine the extent of the intrusion, Gabos said. They will also upgrade the firewalls and take a series of other steps he did not specify.

"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.