Which DDoS attack is described as occurring before the target's vulnerabilities are patched or defensive measures are in place?

• A. Pulse Wave DDoS Attack
• B. Zero-Day DDoS Attack
• C. SYN Flood Attack
• D. ACK and PUSH ACK Flood Attack

Answer: (B)

A zero-day DDoS attack refers to exploiting a vulnerability that is unknown to the vendor and for which no patch or defense exists yet. Because there’s no fix in place, defenders haven’t had a chance to deploy mitigations, so the attack can disrupt services before patches or defenses are available. The other listed techniques describe common DDoS methods that don’t inherently depend on an unpatched vulnerability, so they don’t fit the scenario described. This makes the zero-day approach the best match for “occurring before the target’s vulnerabilities are patched or defensive measures are in place.”