What key step is required for an amplified DDoS attack?

An amplified DDoS attack relies fundamentally on the technique of IP address spoofing to increase its effectiveness. By spoofing the target's IP address, the attacker can make it appear as though the attack traffic is coming from the target itself, rather than from the attacker's actual source. This deceptive tactic allows the attacker to leverage various services that respond to requests with significantly larger amounts of data than they receive. Thus, the attacker effectively amplifies the amount of traffic directed at the target, overwhelming its resources and causing disruption.

In contrast, using brute force login attempts pertains to gaining unauthorized access to accounts and does not contribute to generating traffic for a DDoS attack. Executing a phishing scam involves tricking users into revealing sensitive information, which is unrelated to causing service disruptions through mass traffic. Disabling firewalls might have an effect on overall network security but does not represent a direct mechanism for amplifying the volume of traffic in a DDoS scenario. Therefore, spoofing the target's IP address is the essential action that enables the amplification of the DDoS attack by redirecting larger response traffic to the target.