Personnel work at the Air Force Space Command Network Operations & Security Center at Peterson Air Force Base in Colorado Springs, Colorado July 20, 2010. U.S. national security planners are proposing that the 21st century's critical infrastructure -- power grids, communications, water utilities, financial networks -- be similarly shielded from cyber marauders and other foes. The ramparts would be virtual, their perimeters policed by the Pentagon and backed by digital weapons capable of circling the globe in milliseconds to knock out targets. To match Special Report USA-CYBERWAR/ REUTERS/Rick Wilking (UNITED STATES - Tags: MILITARY SCI TECH POLITICS) - RTXT2UT