UML is one of the most popular modeling languages in today’s industries. This paper works with UML in order to introduce the conceptual O-O model for Internet- based Intrusion Detection Agents. Firstly, we introduce the reason for choosing agent-based technology for Intrusion Detection system. Next, we work on the classification of the proposed Intrusion Detection agents. Last of all, by using a scenario on IP spoofing, we illustrate how the agents work effectively.