Final answer:
Infected machines that perform DDoS attacks are called DDoS attackers. These machines are typically part of a botnet and are controlled by the attacker to overwhelm a target's resources.
Step-by-step explanation:
Infected machines that carry out a DDoS (Distributed Denial of Service) attack are known as B. DDoS attackers. These machines are often part of a larger network of compromised computers called a botnet. Each machine in a botnet is infected with malware that allows the bot herder (the attacker controlling the botnet) to remotely control them and use them to flood the target with traffic, overwhelming the target's resources. This concerted effort makes the services of the target unavailable to its intended users. The other options, such as DDoS victims, defenders, and controllers, represent different roles in the context of a DDoS attack.