This document discusses intrusion detection systems, including their classification techniques and datasets used to implement them. It first defines intrusion detection and intrusion detection systems, explaining that they monitor networks and systems for malicious activity and policy violations. It then categorizes intrusion detection systems as either network-based, host-based, or physical-based. The document also classifies intrusion detection approaches as either signature-based (misuse detection) or anomaly-based detection. It reviews several data mining techniques used for intrusion detection, including classification methods like decision trees, k-nearest neighbors, naive Bayes, and support vector machines. It also discusses clustering techniques. Finally, it mentions some commonly used intrusion detection datasets.