In an effort to strengthen its security procedures, the US Department of Energy (DOE) has shut down the classified computer systems at three nuclear weapons labs, except for those "directly involved in the safety and security support" of the labs, according to Matt Donoghue, a spokesman at the Washington-based agency.
The Sandia National Laboratories in Albuquerque, New Mexico, the Los Alamos National Laboratory in New Mexico, and the Lawrence Livermore National Laboratory in Livermore, California, were affected, he said.
Energy Secretary Bill Richardson ordered "the stand-down," and will announce when it will be lifted, Donoghue said. During the stand-down period, employees will attend training to heighten their awareness about security, he said.
Meanwhile, the Energy Department is considering several measures, such as special access to authorise the transfer of classified files; automated sniffing to discover classified files in e-mail systems; and stricter need-to-know controls, Donoghue said.
No specific incident triggered the action, he said.