1) The document proposes using hidden Markov models to analyze credit card transaction patterns and detect fraudulent transactions. It examines spending profiles of cardholders to identify anomalies compared to normal usage.
2) The key aspects of the proposed system include modeling the different types of purchases as hidden states and transaction amounts as observations in an HMM. The HMM can then detect fraudulent transactions based on deviations from a cardholder's typical spending pattern.
3) Preliminary results show the approach can effectively identify a cardholder's spending profile based on historical transactions and flag transactions inconsistent with that profile as potentially fraudulent.