In cybersecurity terms, a “zero-day” attack refers to an exploit that takes advantage of a previously unknown vulnerability in software, hardware, or network systems before developers can issue a patch or fix. These attacks are particularly dangerous because they leave targets defenseless, often leading to severe consequences. The Netflix series Zero Day borrows this terminology to depict a large-scale cyberattack that cripples U.S. infrastructure, exposing the vulnerabilities of modern states in the face of cyber warfare. Starring Robert De Niro as former President George Mullen, the show explores the vulnerabilities of modern states in the face of sophisticated cyber operations. The series portrays multiple types of cyberattacks, including power grid disruptions, financial sector manipulation, and mass disinformation campaigns—each raising profound legal and geopolitical questions under international law.
The question of whether a cyberattack justifies a state's response with conventional weapons or traditional warfare has long been a contentious topic in international law. The series Zero Day underscores once again that the use of lines of code, rather than bombs or missiles, does not render an attack innocent; in fact, it can lead to destructive impact which is equivalent to that of conventional weapons. Specifically, the potential of cyberattacks to cause casualties, injuries, and property damage has induces states to regulate cyber operations within the established frameworks of traditional warfare.
Given the potential for cyberattacks to cause widespread destruction, an increasing number of states, including NATO institutions, have adopted an "effects-based" approach. Endorsed by the Tallinn Manual 2.0, this approach asserts that a cyber operation may constitute a use of force if it results in significant physical destruction, loss of life, or major economic disruption. Under international law—specifically Article 2(4) of the UN Charter—any use of force that threatens a state’s territorial integrity or political independence is prohibited. While traditional interpretations of force have centered on kinetic military action, legal scholars and governments are increasingly acknowledging that cyberattacks can also violate this fundamental principle.
As one of the most chilling attacks depicted in Zero Day, the cyber operation targeting the national power grid plunges major cities into darkness, causing widespread panic, economic paralysis, and even loss of life due to failing critical infrastructure. Such deliberate attack on the power grid would likely meet the threshold of the use of force, as it endangers public safety and causes severe physical damage and casualties. If the attack is attributable to a foreign state, it could constitute an act of aggression, triggering a potential right to self-defense under Article 51 of the UN Charter.
Beyond power grid sabotage, Zero Day also explores the weaponization of cyber tools for financial manipulation. The series illustrates how hackers exploit vulnerabilities in banking networks, destabilizing financial markets. Although not conventionally viewed as a use of force, such actions could violate international law under the principles of economic coercion and sovereignty. The prohibition of intervention—a well-established norm—prohibits states from coercing another state's essential functions, which could include financial stability. Disrupting stock markets, devaluing currency through artificial intelligence-based attacks, or freezing digital transactions can have effects comparable to traditional economic warfare, further blurring the lines between cyber conflict and conventional aggression.
Another critical aspect of Zero Day is its focus on disinformation campaigns. The series highlights how cyber operatives use deepfake technology and social media manipulation to erode public trust in institutions. While not a direct use of force, this aligns with concerns about foreign interference and sovereignty violations. The lack of physical damage complicates legal responses, but states like France and Norway have suggested that severe cyber disruptions, even without kinetic consequences, may still fall under the prohibition of force if they significantly threaten national security. The potential for deepfakes to manipulate elections or incite violence underscores how cyberattacks extend beyond infrastructure and economic targets to influence the very fabric of democratic governance.
As is often the case with real-world cyber operations, the attacks depicted in Zero Day are frequently carried out through proxies, false flag operations, or decentralized hacking groups with state backing. This complicates efforts to enforce accountability and challenges a state's ability to respond within the legal frameworks of self-defense or countermeasures. The degree of a state's responsibility for a cyberattack depends on the extent of its control over non-state actors and the hierarchical relationship between them, as determined by the legal principles of attribution.
Ultimately, Zero Day is more than just entertainment—it serves as a thought-provoking call for governments and legal scholars to reassess existing frameworks for cyber warfare. As cyberattacks become an increasingly viable instrument of state aggression —often exploiting vulnerabilities stemming from human error, such as the accidental inclusion of a journalist in a Signal group used by top Trump administration officials—the need for clearer legal thresholds and enforcement mechanisms grows ever more urgent. Without decisive legal progress, the events depicted in Zero Day may shift from fiction to a stark preview of future cyber conflicts.
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