A customer paying by phone at a small independent cafe

PAYMENT RISK / CASE STUDY 01

CARDSHIELD

Fraud intelligence without treating every customer like a fraudster.

A bank faces two risks at once: fraud costs money, while blocking genuine payments creates customer friction. CardShield explores how machine learning and decision policy can balance both.

SYNTHETIC DATASETNOT LIVE BANK TRANSACTIONS

Built on synthetic transaction data designed to simulate a realistic fraud workflow.

EXPLORE THE SYSTEM ↓
AN OFFLINE FRAUD DECISION STUDY 01 — 04

02 / HOW THE DECISION WORKS

One payment.
Four layers of judgement.

One payment carries signals. A model estimates risk. A separate policy chooses what happens.

01

PAYMENT SIGNALS

One payment contains many signals.

CUSTOMER · MERCHANT · DEVICE · VELOCITY · LOCATION
02

FRAUD INTELLIGENCE

The model looks for combinations that resemble fraud.

03

RISK

The model estimates how suspicious the payment looks.

Calibration makes that score easier to interpret.
04

DECISION POLICY

The risk signal enters a separate policy. MODEL ≠ POLICY.

APPROVE 89.66% · VERIFY 10.00% · REVIEW 0.32% · DECLINE 0.03%
MODEL ≠ POLICY

The model estimates risk. A separate, cost-aware policy chooses whether to approve, verify, review or decline.

03 / OFFLINE EXPERIMENT

WHAT DID THE SYSTEM ACHIEVE?

Compared with a consistent baseline using held-out synthetic transactions.

~19.77%SIMULATED FRAUD CAPTURE
~20.9%SIMULATED COST REDUCTION
~£906KSIMULATED NET SAVINGS
CONTROLBASELINE POLICY
TREATMENTLOWER EXPECTED COST
−£5.95 / transactionSIMULATED TREATMENT–CONTROL COST DIFFERENCE

150,886HELD-OUT TRANSACTIONS

PASSGUARDRAILS

04 / POTENTIAL APPLICATION

WHERE COULD THIS FIT IN A BANK?

In a real banking environment, a system like CardShield could sit behind card authorization and help prioritize which transactions need intervention.

CARD PAYMENT→RISK ESTIMATE→POLICY→ACTION→MONITORING

POTENTIAL REAL-WORLD APPLICATIONNOT A LIVE BANK DEPLOYMENT

CardShield grew from a fraud-modelling experiment into an end-to-end ML decision system — covering data engineering, risk modelling, policy design, offline experimentation, deployment, monitoring and business reporting.

Built with synthetic transaction data. Financial outcomes are simulated.