During the first US presidential debate in September, both Hillary Clinton and Donald Trump were asked to explain how the escalating threat of cyber warfare would be combatted by their prospective administrations. Clinton, whose candidacy was undermined by a hack on Democratic National Convention emails in July, went immediately on the offensive, accusing Russia of waging cyber-attacks on the US and voicing concern about the increased risk of state-sanctioned intimidation via malicious web leaks. Trump floundered, acknowledging ‘cyber’ – a word that sounded uncomfortably unfamiliar to him – as ‘important’, diagnosing cyber security as ‘hardly doable’, and speculating that a recent raft of high-profile political hacks attributed to Russia, China and North Korea could have been devised by ‘someone sitting on their bed that weighs four-hundred pounds’.

Both candidates would perhaps have done well to watch Alex Gibney’s 2016 documentary Zero Days, a film that doesn’t so much expose the threat of cyber-attacks against the US as it does the US’s role in perpetrating risky attacks of its own, often with alarmingly few safeguards and defences, which put the stability of the world at risk. Judging from the dozens of archival photos in which Clinton appears during Zero Days as Secretary of State, one can only assume she has familiarity with the issue. Then again, what’s also clear from Zero Days is that an issue as complicated and potentially precipitous as cyber warfare wants a hand far steadier than Trump’s.

Alex Gibney is a filmmaker less concerned with filmic style than with how to compress vast and complicated webs of information into a cogent and linear form, and in this regard Zero Days is one of his finest films. After foreshadowing his subject with clips of Iranian state propaganda, the film begins by showing the identification of a cyber-virus by codebreakers Eric Chien and Liam O’Murchu at cyber-security company Symantec, which came to be known as Stuxnet. (Its name is derived from ‘.stub’ and ‘mrxnet.sys’, recurring phrases in the malware’s code.) Revelling in the detail, as layers of dense and mysterious code unfold, Gibney eventually reveals the virus’s ties to Iranian nuclear plants and to plans conceived between the US and Israel to undermine Iran’s nuclear capabilities.

Where Zero Days works best is in explaining to viewers the real-world consequences of mountainous layers of binary code – a difficult and unenviable task – and in linking it to political motivations and the inherent risks of waging warfare in an untested arena. In the case of the Stuxnet virus, we learn, the medical root of the word ‘virus’ is proved alarmingly true – its creators had failed to anticipate its contagious spread around the globe, putting the security of nations at risk if, or more likely when, it lands in enemy hands.

It’s in identifying the ‘enemy’ that Gibney is at his most creative, excitable and outraged. He shows that Israel, headed by then Prime Minister Benjamin Netanyahu, refused to comply with the conditions of its alliance with the US by using Stuxnet against Iran, showing callow disregard for the security of its allies. But Gibney is not content to stop at simple geopolitics. In interviews throughout the film, government officials and intelligence operatives roundly refuse to discuss anything relating to Stuxnet. In a cheekily edited supercut of their responses, one sees multiple faces awash with tension at the very mention of the word. In response to this, Gibney partially invents a character of his own, a female composite character comprised of glitchy particles designed to disseminate classified information whilst protecting the anonymity of the many whistleblowers she represents. We learn from her about the lack of transparency involved in the creation of the US Government’s Cyber Command unit, and its close ties to the troubled NSA, as well as of the paranoid overclassification of information relating to cyber warfare by both the Bush and Obama administrations. What starts as an inquisitive elucidation of a new arena of war becomes an anti-authoritarian exposé of overprotected government secrets, and occasionally lies. On a dime, Gibney’s bad guy shifts from the conventionally villainous Iranian regime to his own government.

Zero Days is of apiece with Gibney’s great whistleblowing exposé We Steal Secrets, about Wikileaks and Chelsea Manning, and along with Laura Poitras’s masterful Citizenfour and Brian Knappenberger’s The Internet’s Own Boy, it forms a new tradition in documentary film that focuses explicitly on the way that the internet is defining the world we live in. These four films, and others like them, attempt to make visual what is based primarily on numerical data. I’m not talking simply about visual representations of code, as in the lines of green binary rolling across a black background made famous by the Wachowskis’ Matrix trilogy, (although this does feature heavily in Zero Days) but more specifically about the way that Gibney and his colleagues explain the palpable truths and realities that these floating numbers in the virtual world represent: the way a line of code, for example, can command a uranium centrifuge in Iran to speed up and explode. By making grave and famously complicated issues lucid with compelling evidence to support it, Gibney has made a film that, more than conspiratorial left-wing charlatanism, can also be considered a public service.

Gibney is also a famously prolific filmmaker, and based on his interests, difficult to pigeonhole. Just last year he directed three detailed documentaries on vastly dissimilar topics:  the popular Scientology exposé Going Clear; the illuminating overview of an increasingly popular cinematic subject with Steve Jobs: The Man in the Machine; and the four-hour, two-part musical biography Frank Sinatra: All or Nothing at All. The speed at which his documentaries, all impeccably researched, are made and released perhaps undermines their ability to be visually inventive. And in terms of visual creativity in documentary, Zero Days does little that can be considered new or interesting. But the journalistic urgency with which Gibney tells this story more than compensates for the areas in which the film lacks. Gibney knows the power of paranoia, and knows better than most the power of pulling the public out from underneath the protection of ignorance. Zero Days, more so than great filmmaking, is a rousing and rattling wake-up call.