See if your information has been exposed in a data breach with our latest free tool Check Now
Finance glossary

What is a zero-day attack?

Bristol James
6 Min

A zero-day attack, also known as a 0-day attack, is a type of cyberattack that exploits recently discovered security vulnerabilities in software or systems. The term “zero-day” indicates that the developers or vendors have had “zero days” to fix the flaw since its discovery by attackers.

What are zero-day attacks?

Zero-day attacks are a type of cyberattack that takes advantage of security vulnerabilities in software or systems unknown to the vendor or developer. The term “zero-day” refers to developers having had “zero days” to fix the flaw since the attackers discovered it. In other words, these vulnerabilities are exploited before developers have had a chance to address them, making them particularly dangerous.

Hackers identify zero-day vulnerabilities by discovering flaws in software that developers are not yet aware of. This gives attackers a window of opportunity to develop exploit code, which they can then use to attack vulnerable systems. Once they gain access, attackers can carry out various malicious activities, such as stealing sensitive data, compromising user accounts, or causing severe system disruptions. This underscores the urgent need for robust cybersecurity measures.

How do zero-day attacks work?

Zero-day attacks often involve socially engineered emails or messages that trick users into performing actions that facilitate malware delivery. For example, an email may appear to be from a legitimate source, prompting the user to open an attachment or click on a link. By doing so, the user unknowingly downloads malware onto their system, allowing attackers to gain unauthorized access.

One of the significant challenges with zero-day attacks is the time it takes for developers to identify and patch the vulnerabilities. It can sometimes take days, weeks, or even months before developers become aware of the vulnerability and release a patch to fix it. During this time, attackers can continue exploiting the vulnerability, putting users at risk. Also, exploits used in zero-day attacks can be sold on the dark web for large sums of money, making them highly sought after by cybercriminals.

Once a vulnerability is discovered and patched, it is no longer considered a zero-day threat. However, the impact of zero-day attacks can be significant, highlighting the importance of proactive cybersecurity measures and prompt patch management to mitigate risks.

What are the types of zero-day attacks?

Zero-day attacks can be classified into targeted and non-targeted zero-day attacks. On the one hand, targeted zero-day attacks are directed towards specific, high-value targets, such as large organizations, government agencies, or prominent individuals. These attacks are meticulously planned and executed to achieve specific objectives, such as stealing sensitive data, disrupting operations, or conducting espionage.

On the other hand, non-targeted zero-day attacks are more widespread and indiscriminate. They exploit vulnerabilities in widely used systems, such as operating systems or web browsers, to affect as many users as possible. While the targets may not be individually selected, the impact can still be significant, potentially causing widespread disruption and compromising the security of numerous individuals and organizations.

Who are the typical targets of zero-day attacks?

Zero-day exploits can target many systems, including operating systems, web browsers, office applications, open-source components, hardware, firmware, and Internet of Things (IoT) devices. Consequently, a diverse range of individuals and entities may fall victim to these attacks:

  1. Individuals who use vulnerable systems. Hackers can exploit security vulnerabilities in operating systems, web browsers, and other software individuals use, potentially compromising their devices and building large botnets.
  2. Individuals with access to valuable business data. Those with access to sensitive business information or intellectual property may be targeted to gain unauthorized access to valuable data.
  3. Hardware devices, firmware, and IoT devices. Vulnerabilities in hardware, firmware, and IoT devices can be exploited to compromise these systems, posing risks to both individuals and organizations.
  4. Large businesses and organizations. Hackers may target large corporations and organizations to steal sensitive data, disrupt operations, or launch coordinated cyber attacks.
  5. Government agencies. Government entities are often targeted due to the sensitive nature of the data they handle and the potential impact of breaches on national security.
  6. Political targets and national security threats. High-profile individuals, political figures, and organizations involved in national security may be targeted for espionage or sabotage purposes.

Regardless of whether an attack is targeted or non-targeted, the consequences can be severe. Zero-day exploits have the potential to impact large numbers of users and organizations, leading to financial losses, reputational damage, and compromised security. Even users who are not explicitly targeted may inadvertently suffer collateral damage from these exploits, highlighting the pervasive threat of zero-day attacks.

How to identify zero-day attacks

Identifying zero-day attacks poses a significant challenge due to the diverse nature of zero-day vulnerabilities, which can manifest in various forms: missing data encryption, broken algorithms, password security issues, and more. On top of this difficulty, there is the issue of the limited availability of detailed information about zero-day exploits until they are identified.

To detect zero-day attacks, several techniques are employed:

  1. Malware databases. Some detection methods rely on existing databases of known malware and their behaviors as a reference point. While these databases are updated frequently and serve as valuable resources, they have limitations when it comes to zero-day exploits, which, by definition, are new and unknown.
  2. Behavior-based analysis. Alternatively, some techniques focus on identifying zero-day malware characteristics based on their interaction with the target system. Instead of analyzing the code of incoming files, this approach observes their interactions with existing software to determine if they exhibit malicious behavior.
  3. Machine learning. Machine learning algorithms are increasingly used to detect zero-day attacks by analyzing data from previously recorded exploits. Machine learning models can identify deviations indicative of potential zero-day exploits by establishing a baseline for safe system behavior derived from past and current interactions. The accuracy of detection improves with the availability of more data.
  4. Hybrid detection systems. Often, a combination of different detection systems is employed to enhance the overall effectiveness of zero-day attack detection. By leveraging multiple detection techniques in tandem, organizations can strengthen their ability to effectively identify and mitigate zero-day threats.

In general, detecting zero-day attacks requires a multifaceted approach combining various detection methods, including malware databases, behavior-based analysis, machine learning, and hybrid detection systems. By continuously evolving detection capabilities and leveraging innovative technologies, organizations can bolster their defenses against emerging threats posed by zero-day exploits.

How to prevent a zero-day attack

Preventing zero-day exploits and attacks requires proactive measures to mitigate risks and enhance cybersecurity resilience:

  1. Patch management. Establish a formal patch management program to ensure timely application of security patches released by vendors in response to zero-day vulnerabilities.
  2. Vulnerability management. Conduct thorough vulnerability assessments and penetration tests to identify potential zero-day vulnerabilities within organizational systems before malicious actors exploit them.
  3. Attack Surface Management (ASM). Utilize ASM tools to comprehensively assess network assets and vulnerabilities from a hacker’s perspective, facilitating the early detection of zero-day vulnerabilities.
  4. Threat intelligence feeds. Stay updated on external threat intelligence sources to promptly receive alerts from security researchers and industry experts about newly discovered zero-day vulnerabilities.
  5. Zero-trust architecture. Adopt a zero-trust approach to network security, implementing continuous authentication and least privilege access controls to limit the impact of zero-day exploits and prevent lateral movement by malicious actors within the network.

By implementing these preventive measures, organizations can enhance their resilience against zero-day exploits and minimize the potential impact of these advanced cyber threats on their systems and data.


  • Zero-day attacks exploit vulnerabilities in software or systems that developers haven’t yet patched. These attacks can lead to unauthorized access, data theft, or disruption of system operations.
  • Targets of zero-day attacks include individuals, businesses, government agencies, and political entities.
  • Detecting zero-day attacks requires advanced methods like behavior-based analysis and machine learning.
  • Preventing zero-day attacks involves proactive measures like patch management and vulnerability assessment.

Related articles

The new security standard for business payments

Eftsure provides continuous control monitoring to protect your eft payments. Our multi-factor verification approach protects your organisation from financial loss due to cybercrime, fraud and error.