Understanding the Basics of DDoS Attacks. Refer to this illustration: Behind a Client is a person that orchestrate an attack. A Handler is a compromised host with a special program running on it. Each handler is capable of controlling multiple agents. An Agent is a compromised host that runs a special program. Each agent is responsible for generating a stream of packets that is directed toward the intended victim. Attackers have been known to use these four programs to launch DDoS attacks: Trinoo.