N.S.A. Breached North Korean Networks Before Sony Attack, Officials Say - NYTimes.com

More cyber spy-vs-spy details

"But fearing the exposure of its methods in a country that remains a black hole for intelligence gathering, American officials have declined to talk publicly about the role the technology played in Washington’s assessment that the North Korean government had ordered the attack on Sony.

The extensive American penetration of the North Korean system also raises questions about why the United States was not able to alert Sony as the attacks took shape last fall, even though the North had warned, as early as June, that the release of the movie “The Interview,” a crude comedy about a C.I.A. plot to assassinate the North’s leader, would be “an act of war.”"

N.S.A. Breached North Korean Networks Before Sony Attack, Officials Say - NYTimes.com