What Is a Zero-Day Attack?

What Is a Zero-Day Attack?

6 Min.

A zero-day attack is a type of software attack that takes advantage of a weakness that the vendor or developer did not know existed. The name of the problem is based on the number of days that a software developer has been aware of it. To address a zero-day attack, a software patch is the solution. Antivirus software and regular system updates can help prevent zero-day attacks, although this is not always guaranteed. There are various markets for zero-day attacks, some of which are legal while others are illegal.


Zero-day attacks, alternatively known as Day Zero assaults, represent a formidable breed of cyber threats that capitalizes on an undisclosed software security flaw, unbeknownst to the software vendor or developer. This clandestine vulnerability requires immediate attention from the developer to mitigate potential risks for software users. The developer's swift resolution comes in the form of a software patch aimed at curtailing the imminent danger. Intriguingly, zero-day attacks extend their reach to the Internet of Things (IoT) realm, enabling malevolent actors to orchestrate attacks on this interconnected web of devices. This nomenclature, "zero-day attack," stems from the precise measure of time denoting the extent of awareness the software developer possesses concerning the issue at hand.

What Is a Zero-Day Attack?

In cybersecurity, a zero-day attack encompasses a range of insidious tactics, including malware, adware, spyware, or unauthorized access to sensitive user information. To fortify their defenses against such attacks, users are advised to enable automatic updates for their software, spanning operating systems, antivirus software, and internet browsers. Additionally, promptly installing recommended updates outside of regular schedules is crucial.

Nevertheless, relying solely on updated antivirus software does not guarantee protection against zero-day attacks. This stems from the fact that until a software vulnerability becomes publicly known, antivirus software may lack the means to detect it. Augmenting the arsenal against such assaults, host intrusion prevention systems prove invaluable by forestalling and warding off intrusions while safeguarding critical data.

Imagining a zero-day vulnerability as an unbeknownst unlocked car door, the owner's false belief in its security exposes an opportunity for an opportunistic thief. Undetected, the thief gains entry, pilfering valuables from the car owner's glove compartment or trunk, leaving the victim oblivious until days later when the damage is done, and the thief has vanished into the shadows.

Although criminal hackers are notorious for exploiting zero-day vulnerabilities, government security agencies also capitalize on them for surveillance or offensive maneuvers. This heightened demand from government entities fuels a thriving market for exchanging information regarding these vulnerabilities and their exploitative techniques.

Zero-day exploits can be kept secret, shared with the software vendor, or sold to a third party. In cases of sale, these exploits may be accompanied by or devoid of exclusive rights. Ideally, software companies responsible for security flaws rely on ethical hackers or white hats to privately disclose vulnerabilities, enabling prompt remediation before malicious actors take advantage. However, certain vulnerabilities necessitate the collective efforts of multiple parties to achieve a comprehensive resolution, rendering complete private disclosure an elusive goal.

Zero-Day Markets: Unveiling the Intricacies of Exploits

Within the clandestine realms of the zero-day information market, criminal hackers thrive on exchanging intricate details that unlock vulnerable software, granting access to coveted information. Meanwhile, the gray market serves as a platform for researchers and companies to trade such information with militaries, intelligence agencies, and law enforcement entities. In contrast, the white market operates on a different paradigm, where companies enlist the aid of white hat hackers and security researchers to uncover and divulge software vulnerabilities to developers, enabling timely fixes before criminal hackers can exploit them.

The value of zero-day information fluctuates depending on various factors, including the buyer, seller, and level of usefulness. Ranging from a few thousand to several hundred thousand dollars, the market presents an enticing avenue for potential gains. Before any transaction can be finalized, sellers are required to furnish proof-of-concept (PoC) as evidence of the existence of the zero-day exploit. For those seeking discreet exchanges, the Tor network provides an anonymous platform, while Bitcoin facilitates the seamless completion of zero-day transactions.

While zero-day attacks exude an aura of imminent danger, their actual threat level may be more nuanced. Governments often possess alternative means to surveil their citizens, and zero-day exploits may not be the most effective avenue to exploit businesses or individuals. Deploying an attack strategically and covertly, without the target's awareness, maximizes its impact. An indiscriminate unleashing of a zero-day attack on a vast network of computers risks exposing the vulnerability prematurely, triggering quick patch releases that hinder the attackers from achieving their ultimate objectives.

Real-Life Instances: Unveiling Zero-Day Exploitations

Microsoft Word's Battle

Back in April 2017, Microsoft found itself embroiled in a zero-day attack involving its widely used Microsoft Word software. Exploiting a vulnerable and unpatched version, the attackers infiltrated the system using the insidious Dridex banker trojan. By embedding malicious code within Word documents, the trojan seamlessly executed its payload upon document opening. Although the attack was discovered by McAfee, an antivirus vendor, and promptly reported to Microsoft, it had already affected millions of users, with the campaign stretching back to January.

Chrome's Vulnerability Voyage 

More recently, Google's Chrome web browser faced a series of attack vectors and exploits. In 2022 alone, Google issued no less than four urgent notifications urging Chrome users to update their browsers. These cautionary appeals responded to a string of zero-day attacks that put user security at risk.

Sony Pictures Hack

One of the most well-known cases is the 2014 Sony Pictures hack. This audacious cyber assault exploited an undisclosed vulnerability, enabling the installation of covert malware. Unbeknownst to Sony, the malware swiftly targeted and tampered with critical files about upcoming films, inflicting extensive financial losses amounting to millions of dollars. The incident further tarnished Sony's reputation, exposing perceived security vulnerabilities. The attack is widely believed to have been orchestrated by North Korean agents in retaliation for the release of "The Interview," a satirical film mocking the leader of North Korea, Kim Jong Un. This highly publicized event captured global attention, accentuating the ever-present dangers posed by zero-day vulnerabilities in the cyber landscape.


Zero-day attacks pose a significant cybersecurity challenge, exploiting unknown software vulnerabilities. Antivirus software and updates provide some protection but not foolproof. Zero-day information markets involve legal and illegal exchanges. Real-world examples include the Microsoft Word attack, Chrome vulnerabilities, and the notorious Sony Pictures hack. Vigilance and proactive measures are crucial in combating the persistent threat of zero-day attacks.

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