Fraud detection is a classic adversarial analytics challenge: As soon as an automated system successfully learns to stop one scheme, fraudsters move on to attack another way. Each scheme requires looking for different signals (i.e. features) to catch, is relatively rare (one in millions for finance or ecommerce, for example), and it may take months to investigate a single case (in healthcare or tax, for example) – making quality training data scarce. This talk will cover, via live demo & code walk-through, the key lessons we’ve learned while building such real-world software systems over the past few years. We’ll incrementally build a hybrid machine learned model for fraud detection, combining features from natural language processing, topic modeling, time series analysis, link analysis, heuristic rules & anomaly detection. We’ll be looking for fraud signals in public email datasets, using Python & popular open-source libraries for data science and Apache Spark as the compute engine for scalable parallel processing.