A pixelated “whistleblower” in “Zero Days.” The documentary from Alex Gibney (“Taxi to the Dark Side”) explores the Stuxnet virus and finds secret, far-reaching cyberwarfare. (Magnolia Pictures)

The first rule of Fight Club is: You do not talk about Fight Club. Similarly, all around us, just out of plain sight, secret cyberwarfare is raging everyday, and this murky world is brought to light in Alex Gibney’s chilling documentary “Zero Days.”

A dizzying compendium of political and nuclear history, modern-day politics, computer-science facts and righteous outrage, this thoroughly researched film is designed to spur a public outcry. Few will emerge from its story of intelligence tradecraft and egregious lapses in oversight without feeling seriously freaked out. “The worm is loose!” former CIA director Michael Hayden says playfully at one point in “Zero Days.” Ha ha.

The nominal subject of “Zero Days” is Stuxnet, a malicious computer virus that incapacitated Iran’s nuclear centrifuges in 2009 and 2010, and that has since spread to computer systems in several other countries. Doggedly reporting out how and why the virus was created, Gibney tracks down Eric Chien and Liam O’Murchu, the heroic young cyber-sleuths at Symantec who were chiefly responsible for identifying the code and following its bread-crumb trail to the United States and Israel. He elicits sobering analyses and predictions from New York Times security reporter David Sanger and a passel of nuclear and cybersecurity experts, as well as Hayden, Richard Clarke and other intelligence officials. Although persuasive evidence points to the United States and Israel as Stuxnet’s authors — and Israel as the party whose rash decisions pushed it into the open — not one official will confirm or deny anything.

That dubious Fight Club ethic extends to Israel’s own nuclear program, which goes curiously unexamined in “Zero Days.” Notwithstanding that omission, the film conveys a convincing sense of urgency, especially when Gibney is interviewing his star subject, a mysterious “whistleblower” disguised by way of high-tech computer graphics that pop and pixelate with menacing beauty.

Although “Zero Days” is overlong, with the numbing number of visual and verbal data points inevitably collapsing of their own weight, the Stuxnet story finally plays out like a twisty summer espionage thriller, with Gibney amping up that drama with sleek digital imagery and a foreboding musical score. The real source of his outrage, though, is more prosaic and more crucial, which is the epidemic of over-classification in the U.S. government, and its implications for democratic consent. (Congress is conspicuously absent in the film, save for a couple of ceremonial hearings.)

“Zero Days” could be interpreted as a bookend to Gibney’s “We Steal Secrets,” the 2013 movie about WikiLeaks, but it’s really a continuation of his finest film, the Academy Award-winning 2007 documentary “Taxi to the Dark Side,” about the use of torture during the war in Afghanistan. It turns out we’re all in Fight Club, but only a few of us know to what extent, and to what potentially disastrous effect.

PG. At Landmark’s E Street Cinema. Contains coarse language. 116 minutes.