Review: Alex Gibney's latest documentary skillfully details damage done by tech warfare

The title of "Zero Days," Alex Gibney's chillingly astute glimpse into the shadowy world of global cyber warfare, refers to what is known as a zero-day vulnerability -- a security gap in a piece of software or hardware that, once exploited for the purposes of an attack, leaves the defender no time to respond. But the term also carries a less technical, more intuitive meaning. The future is now, Gibney's documentary persuasively argues, and what it holds for all of us is as scary to contemplate as it may be impossible to ward off.