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Security Operations · Foundational

Zero-Day Vulnerability

A vulnerability unknown to the vendor or without an available patch, which attackers may exploit before defenders can fix it.

Definition

Zero-days are valuable to attackers and are often used by nation-states and sophisticated criminals. Defenses rely on layered controls, behavioral detection, exploit mitigations, segmentation and rapid vendor response. Once a patch is released, unpatched systems are vulnerable to "n-day" exploitation.

Example

Attackers exploiting an undisclosed flaw in a file transfer appliance to steal data from hundreds of organizations.

Exam tip

Signature-based tools cannot detect zero-days; choose behavior-based or defense-in-depth answers.

Don't confuse it with

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