Nation-statesare a growing threat to U.S. critical infrastructure and have the ability toinflict major damage on systems including the electric power grid, the highestmilitary official in charge of cyber security told a U.S. Senate committee.

"Overthe last year we've seen an increase of cyberspace operations by state andnon-state actors," Admiral Michael Rogers, commander of the U.S. CyberCommand and director of the National Security Agency, said at an April 5hearing before the U.S. Senate Armed Services Committee. Although thegovernment has seen a "wide range of malicious cyber activities"aimed at government and private sector targets, "nations still representthe greatest threats" to U.S. cybersecurity, Rogers said.

CommitteeChairman John McCain, R-Ariz., asked if Russia had the capability to inflict "seriousharm" on U.S. critical infrastructure, such as the electric grid. Rogerssaid Russia and, to a lesser extent, China have that ability, noting taht thelatter is still engaged in cyber activities against U.S. companies after Chinarecently breached the U.S. Office of Personnel Management's networks.

Russia,however, is of more immediate concern, particularly after a December 2015cyberattack on partof Ukraine's electric grid that left about 225,000 customers without power overa period of several hours. McCain squarely blamed Russia for the attack,although the country has not confirmed any responsibility for the event.

Rogerssaid Russia had the greatest cyberattack capabilities, followed by China, Iranand North Korea. But he noted Iran's abilities, although they are improving,have been targeted less at U.S. infrastructure and companies recently. InMarch, a grand jury indictedseven Iranians for cyberattacks on the U.S. financial sector and a dam in theNew York City area between December 2011 and May 2013.

Rogersurged more funding and personnel to bolster U.S. cyber defense. Committeemember Sen. Angus King, I-Maine, said it was "impractical and almostimpossible" for Rogers to head both the NSA and Cyber Command and alludedto a likely separation of the two organizations, but Rogers said "we'rejust not ready to do that today." McCain said he would likely propose thatthe U.S. Cyber Command be run as an independent combatant command as part ofthe Department of Defense's authorization bill. Acombatant command is a segment of the Department of Defense with forces from atleast two military departments and a broad, continuing mission.