Obama, rapping Putin, says U.S. could strike back on cyber

President Barack Obama has put Russia's Vladimir Putin on notice that the U.S. could use offensive cyber muscle to retaliate for interference in the U.S. presidential election, his strongest suggestion to date that Putin had been well aware of campaign email hacking."Whatever they do to us, we can potentially do to them," Obama declared Friday.Caught in the middle of a post-election controversy over Russian hacking, Obama strongly defended his administration's response, including his refusal bef