U.S. strategic nuclear weapons and the command systems that control them are vulnerable to cyber attacks although most are hardened against many types of electronic attacks, the commander of the U.S. Strategic Command said on Tuesday. 

Air Force Gen. C. Robert Kehler said during a hearing of the Senate Armed Services Committee that nuclear weapons and the communications used to control them are older and thus less vulnerable to disruption by computer network attacks. 

"However, we are very concerned with the potential of a cyber related attack on our nuclear command and control and on the weapons systems themselves," Kehler said. "We do evaluate that." 

The four-star general was responding to questions about the security of nuclear controls outlined in a Defense Science Board report. 

The report from January stated that U.S. nuclear forces are regularly assessed for their reliability and readiness but said "most of the systems have not been assessed against a sophisticated cyberattack to understand possible weak spots." 

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