A ________ attack is an attack that is made before attack signatures for the threat are defined.

• A. Zero-Day
• B. Vulnerability Based
• C. Stealth
• D. Anomaly Based

Answer: (A)

This question is about attacks that occur before defenders have any signatures to identify them. A zero-day attack happens when an attacker exploits a vulnerability that is unknown to the security community, so there are no patches and no attack signatures for that threat yet. Because signature definitions haven’t been created for it, this type of attack happens prior to any signature-based detection being available.

The other ideas describe different concepts. A vulnerability-based scenario relies on known weaknesses and often known exploits or patches, not the absence of signatures for a new threat. Stealth refers to the attacker’s goal of avoiding detection, not specifically the timing relative to signature creation. Anomaly-based detection, on the other hand, looks for unusual behavior rather than matches to known signatures, so it isn’t defined by the lack of attack signatures for a threat.