IP spoofing is often used as part of which of the following?

IP spoofing is a technique where an attacker sends IP packets from a false "spoofed" source address in order to disguise their identity or impersonate another computing system. This method is frequently employed as part of denial-of-service attacks. In these attacks, the goal is often to overwhelm a target system or network with a flood of traffic. By using IP spoofing, attackers can obscure their actual source and make it more difficult for defenders to mitigate the attack or identify the perpetrator.

In the context of denial-of-service attacks, the attacker can generate a large volume of requests to a target from multiple fake IP addresses, thus amplifying the attack's scale and complicating the response. The use of spoofed addresses makes it challenging to block the incoming traffic effectively or trace it back to the actual source, thereby increasing the attack's efficacy.

The other options, while they may involve malicious activities, do not typically leverage IP spoofing in the same manner or to achieve the same objectives as denial-of-service attacks.