Cybersecurity is evolving very rapidly, and some security flaws are particularly dangerous. Among them are zero-day vulnerabilities and zero-click vulnerabilities.
In this article, we will clearly explain the difference between these two types of vulnerabilities, understand why they represent a significant risk, and see how to protect against them effectively.
What Is a Zero-Day Vulnerability?
A zero-day vulnerability is a security flaw in software that its vendor is not yet aware of. This means that at the moment the flaw is discovered — and sometimes exploited — no patch is available yet.
This flaw can affect an operating system, an application, or a web service. The term zero-day attack is used when an attacker exploits this vulnerability before the developer has had time to release a security update.
In reality, a zero-day vulnerability can exist in software from the moment it is released. It can remain hidden for days, months, or even years without anyone noticing.
In the best-case scenario, cybersecurity researchers or the developers themselves discover the flaw and fix it quickly. However, cybercriminals may also find it first and use it to attack systems.
That is why zero-day vulnerabilities are particularly dangerous: they can be exploited while no official protection yet exists.
What Is a Zero-Click Vulnerability?
Zero-click vulnerabilities represent another major threat. Unlike traditional phishing or social engineering attacks, they require no action from the victim. No click, no download, no attachment opened.
The attack executes automatically through a message, a VoIP call, or a notification. This means that simply receiving a message can be enough to compromise a device.
Zero-click vulnerabilities are especially dangerous because they can infect devices in the background and remain undetected by traditional antivirus solutions.
Zero-Day Vulnerabilities vs Zero-Click Vulnerabilities: What’s the Difference?
Although often confused, zero-day vulnerabilities and zero-click vulnerabilities are not the same.
| Type | Description | Exemple |
|---|---|---|
| Zero Day Vulnerabilities | Unknown software flaw | Unpatched software exploited in a zero-day attack |
| Zero Click Vulnerabilities | Exploitable flaw without user interaction | Messages, calls, or notifications used to launch an attack |
An attack can combine both: it may use a zero-day vulnerability exploited through a zero-click vulnerability, making the attack extremely dangerous and difficult to detect.
How to Protect Against Zero-Day and Zero-Click Vulnerabilities
Even if a zero-day vulnerability is initially unknown, certain measures can significantly reduce the risks. Regular system updates are essential, as patches are released once the flaw is identified.
Enabling advanced protections such as process isolation, sandboxing, and memory protection mechanisms (ASLR, DEP) strengthens system resilience. Using EDR or XDR solutions also helps detect abnormal behavior, even without a known signature.
Finally, adopting a Zero Trust approach and segmenting your network limits the impact of a potential compromise.
Conclusion
Zero-day vulnerabilities and zero-click vulnerabilities are among the most sophisticated threats in cybersecurity today. They highlight the importance of a proactive and multi-layered security approach.
Staying informed about new vulnerabilities, keeping systems up to date, adopting advanced protection solutions, and following a Zero Trust strategy are best practices for defending against these invisible threats.
Understanding and anticipating zero-day vulnerabilities and zero-click vulnerabilities is essential for any company, developer, or security professional seeking to reduce the risk of a zero-day attack in their environment.