The hacking of Sony Pictures was not an act of war but a "very costly" act of vandalism, President Barack Obama said in an interview airing Sunday. "We take it very seriously and we will respond proportionally," the president said in an interview on CNN's "State of the Union." The FBI has formally accused North Korea of the hacking attack that led movie theater chains around the United States to cancel its comedy "The Interview," which depicts an assassination attempt of North Korean leader Kim Jong Un.