In which attack does an attacker infect multiple systems, referred to as "zombies," to carry out an attack on a target?

The scenario described involves an attacker infecting multiple systems, commonly referred to as "zombies," to launch an attack on a target. This aligns closely with the nature of a Distributed Denial of Service (DDoS) attack. In a DDoS attack, numerous compromised systems (the "zombies") are used to flood the target with overwhelming amounts of traffic, causing the target system to slow down, crash, or become unable to respond to legitimate requests.

The essence of a DDoS attack is the distributed nature of the attack solutions, which sets it apart from a standard Denial of Service (DoS) attack that typically originates from a single source. The distributed aspect is crucial because it complicates defensive measures and makes it challenging to mitigate the attack effectively. This is why the choice of a DDoS attack is the most accurate in this context.

In contrast, the other options such as Identity Spoofing and Man-in-the-Middle attacks focus on different types of infractions that involve deception or interception rather than overwhelming multiple systems to disrupt a service. Therefore, the focus on infecting numerous machines to create a coordinated attack clearly identifies the act as a Distributed Denial of Service.