Anomaly detection: A survey
            
        
            
    
    
                
            Chandola, V., Banerjee, A., & Kumar, V. (2009). Anomaly detection: A survey. ACM Computing Surveys, 41(3), 1–58.
Read Sections 1–5 for an in-depth overview of anomaly detection methods, including classification-, clustering-, and nearest neighbor-based techniques. This survey provides broad coverage of application areas and challenges in detecting anomalies.