Email Fraud Detection Pipeline
Tri-Stream Stacking Ensemble + Deep AutoencoderAn end-to-end fraud classification architecture built on 447K Enron emails to resolve an extreme 192:1 class imbalance. Incorporates a custom PyTorch Deep Autoencoder to compress 384-dimensional MiniLM embeddings into 64-dimensional latents and derive unsupervised anomaly reconstruction error signals, stacked with a Tri-Stream Level-1 GBDT ensemble and an ElasticNet meta-learner.
System Specifications:
- PyTorch Autoencoder: 384-d MiniLM compressed into 64-d latents + unsupervised anomaly MSE reconstruction signal.
- Tri-Stream Level-1 Models: Stream A (GPU XGBoost), Stream B (CatBoost with native text dictionaries), Stream C (LightGBM on TF-IDF n-grams).
- Level-2 Stacking Meta-Learner: ElasticNet meta-learner in logit space with 12 skip-connection domain features (VADER polarity, stylometry, sender velocity).
- Dynamic Threshold Tuning: tau* = 0.050 achieving 0.8842 F2-score, 90.5% recall, 80.8% precision, and 0.999 ROC-AUC.