What is Zero Day Malware?

Zero day malware is malware that exploits unknown and unprotected vulnerabilities. This novel malware is difficult to detect and defend against, making zero day attacks a significant threat to enterprise cybersecurity.

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Zero Day Vulnerabilities and Zero Day Malware

Zero day vulnerabilities are ones that are exploited in the wild before the software manufacturer has the opportunity to release a patch or before that patch is widely deployed. The delays associated with patch management leave a window – called “day zero” – where the vulnerability can be exploited in organizations without access to the proper defenses.


Zero day malware is malware that takes advantage of these zero day vulnerabilities. Often, exploit developers can create attacks against vulnerabilities more quickly than the corresponding patches can be developed and deployed. This means that malware exploiting vulnerabilities can spread widely before organizations can clamp down on the threat.

Examples of Zero Day Malware

For zero day malware to exist, a zero day vulnerability needs to exist as well. Unfortunately, these types of vulnerabilities are very common.


A recent example is a set of vulnerabilities in Microsoft Exchange that were patched by the company in March 2021. These vulnerabilities could be exploited to allow an attacker to run malicious code on vulnerable systems – a remote code execution (RCE) vulnerability – which makes them perfect for zero day malware. However, despite the significant potential impact of the vulnerabilities, patching was slow.


This resulted in the creation of a number of different zero day malware variants that exploited the vulnerabilities. One of these zero day malware variants is called Hafnium. Hafnium is an information stealing malware that uses the Microsoft Exchange exploits to gain access to vulnerable Exchange servers. From there, it elevates its privileges and uses the resulting access to steal emails and user credentials.

Why Traditional Cybersecurity Strategies Are Ineffective Against Zero Day Malware

Zero day malware is such a significant cybersecurity challenge because many traditional cybersecurity strategies are incapable of protecting against it. Since zero day malware is released shortly after a particular vulnerability has been discovered – and before much is known about it or patches are developed – traditional defenses can struggle to detect and defend against it.


Some cybersecurity strategies are based upon knowledge of the vulnerability or exploit in question, which obviously is not available for zero day threats. As a result, certain methods for mitigating these threats are ineffective, such as:


  • Patch Management: The best way to mitigate the threat of a particular malware variant is to patch the vulnerability that it relies upon. However, with zero day malware, patches are not available, making it impossible to apply them to vulnerable systems.
  • Signature-Based Detection: Many traditional antivirus and threat detection systems work using signatures, which are unique fingerprints of a malware variant. With zero day malware, cybersecurity researchers have not had the opportunity to study the malware and develop and distribute these signatures.
  • Exploit Detection: In addition to malware, it is also possible to detect exploitation of vulnerabilities using signatures. However, like the malware, zero day vulnerabilities lack the signatures needed for this to work.


Cybersecurity is always a race between cyber defenders and exploit developers. In the case of zero day vulnerabilities and malware, exploit developers have a significant advantage if organizations rely on traditional methods for threat management.

How to Prevent Zero Day Malware

The traditional cybersecurity strategies that are ineffective against zero day malware rely heavily on detection. However, it is difficult to accurately detect and respond to a threat that you don’t know exists.


A better approach to managing the zero day threat is to use prevention. Check Point’s prevention-first approach is the only way to effectively protect against unknown threats and includes features such as:


  • Threat Intelligence: Threatcloud is the largest cyber threat intelligence database, which uses AI to inspect 86 billion transactions each day. This enables it to detect zero day malware campaigns early, empowering organizations to protect themselves.
  • Threat Prevention Engines: While malware variants can differ significantly, they often use similar techniques to achieve their goals. Threat prevention engines monitor for red flags – such as the use of return oriented programming (ROP) or code from known malware – to detect and block zero day malware.
  • Consolidation: During a zero day malware attack, a rapid and coordinated response is essential to minimizing the impact and cost of the incident. Check Point solutions consolidate an organization’s security architecture, enabling coordinated and automated responses against rapidly-evolving threats.


Check Point’s use of artificial intelligence (AI) is critical to its prevention-focused security strategy. To learn more about how AI helps to prevent cyberattacks, check out this whitepaper.

Getting Started with Zero Day Prevention

A clear understanding of your organization’s current security posture is essential for improvement. To take the first steps toward preventing zero day attacks, take Check Point’s free security checkup.


Another good step is to focus security efforts on your most vulnerable assets. For many organizations, this is now their remote workforce. You’re welcome to sign up for a demo to learn how Check Point can help to protect your remote employees from zero day malware attacks.

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