The document discusses different approaches for anomaly-based network intrusion detection systems (NIDS), including machine learning, fuzzy logic, and genetic algorithm approaches. Specifically, it summarizes: 1) Fuzzy logic based NIDS that uses a strategy to automatically generate fuzzy rules from training data to define normal network behavior and detect anomalies. Experiments using the KDD Cup 99 dataset showed it achieved 90% accuracy. 2) The use of genetic algorithms for NIDS, which encode network data as chromosomes and use selection/evolution principles to optimize detection of intrusions based on fitness metrics like packet drop rates. 3) Research applying fuzzy logic and genetic algorithm techniques to detect packet dropping attacks by malicious nodes in mobile ad hoc