This week, security experts warned that a new computer virus could cause mass power outages — a scenario that could prompt life-and-death emergencies across the globe. The assessment comes after a recent attack on a power plant in Kiev — and only a few a few years after the 2010 Stuxtnet attack, which aimed to destroy centrifuges inside Iran’s nuclear facilities. On this episode, I talk to Oscar-winning director Alex Gibney about his new film “Zero Days,” which reviews the Stuxtnet attack. He says that the United States is keeping its involvement in cyberweapons a secret — and that such weapons could easily be turned around to attack America in ways that could cause mass casualties. Gibney also asserts that in keeping its cyberwarfare programs secret, the U.S. government is preventing Americans from openly debating whether there should be restrictions on these weapons — and whether they present a grave threat to the nation.