NimbusPay Fraud Detection

NimbusPay is a digital payments company. This tool scores transactions for fraud risk and summarizes chargeback exposure by risk tier.

Quick start

pip install -r requirements.txt
python analyze_fraud.py
pytest

Files

File	Purpose
analyze_fraud.py	Main pipeline: loads data, scores transactions, prints report
features.py	Feature engineering: merges accounts, flags large amounts and login pressure
risk_rules.py	Scoring logic: score_transaction (0–100) and label_risk (low/medium/high)
test_risk_rules.py	Pytest tests for scoring and labeling functions
transactions.csv	Raw payment transactions
accounts.csv	Account-level data including prior chargeback history
chargebacks.csv	Confirmed fraud chargebacks used to validate rule performance

Risk signals

Signal	Low risk	Elevated	High
Device risk score	< 40	40–69	≥ 70
Transaction amount	< $500	$500–999	≥ $1,000
Transactions in 24h	< 3	3–5	≥ 6
Failed logins in 24h	0	2–4	≥ 5
Prior chargebacks	0	1	≥ 2
International	No	—	Yes