The story quoted Mason as describing the attack as a sophisticated Advanced Persistent Threat (APT), designed to gain a foothold on the lab's networks and then to quietly looking for and steal specific types of information.

"If you look at this APT, it is much more sophisticated than what was being used a few years ago," Mason told Konxnews.com. "Certainly what we've seen is very consistent with the RSA attack," he said referring to an that resulted in data relating to the company's SecurID two-factor authentication technology being stolen.

Almost all of the lab's 200 IT staff are currently engaged in either investigating the attacks or ensuring that other systems remain available, Penland said. Staff from other national laboratories, are also helping in the investigations, she said. At the moment, the attacks are the subject of an IT investigation only and not a criminal one.

Penland said that the attacks appear to have been directed at ORNL's business systems. The lab's supercomputers, including the world's most powerful system, the 1.75-petaflop Jaguar, have been unaffected by the attacks and continue to operate normally.

As of this afternoon, the attacks appear to have been contained, she added. "Keeping the Internet down is a precaution to make sure that nothing gets out as we investigate further," she said.