The paper presents an approach to design a cyberworld intended for the research of security systems functioning in the Internet. These systems are represented as the complex of various interacting teams of intelligent agents. The agents can be in the state of antagonistic counteraction or cooperation. The general conceptual model of agent teams? antagonistic counteraction and cooperation is suggested. The task of developing the agent cyberworld, where agents realize the distributed attacks and defense, is investigated on the example of "distributed denial of service" attack subject domain. The architecture and implementation of research environment for agentoriented simulation is presented. The environment is implemented on the basis of discrete-event simulation system that allowed to combine the agent-oriented and network protocol based simulation.