fraud-detection（欺诈检测）

Fraud Detection

Overview

Payment fraud costs e-commerce merchants 2–3% of revenue through chargebacks, lost goods, and dispute fees. Effective fraud detection layers platform-native risk scoring, 3D Secure authentication, velocity checks, and manual review queues for suspicious orders. The right approach depends on your platform — Shopify includes a built-in fraud analysis tool, while WooCommerce and BigCommerce require a dedicated fraud prevention service or payment processor's fraud tools.

When to Use This Skill

• When chargeback rates exceed 0.5% of transaction volume (Visa's threshold for "excessive" disputes is 0.9%)
• When launching in a new market with unfamiliar fraud patterns
• When selling high-value, easily resold goods (electronics, gift cards, luxury items)
• When you observe account takeover patterns, card testing, or bulk bot purchases
• When building or auditing a checkout flow that processes card-not-present transactions

Core Instructions

Step 1: Determine the merchant's platform and choose the right fraud tools

Step 2: Enable and configure platform-native fraud tools

Shopify

Shopify includes a Fraud analysis indicator on every order based on signals like IP/billing address mismatch, card verification failure, and known fraud patterns.

Reviewing fraud indicators:

1. Open any order in Shopify admin
2. Click Fraud analysis in the order details panel
3. Shopify shows a risk level (High / Medium / Low) with specific reasons (e.g., "Card verification value failed", "IP and billing address country differ")

Configuring fraud response rules:

1. Go to Settings → Payments → Fraud prevention (if using Shopify Payments)
2. Enable Automatic review for orders flagged as high risk — Shopify will hold these orders and send you an email
3. Set Automatically cancel for orders Shopify deems highest risk

Signifyd (Shopify App Store — Guaranteed Fraud Protection): Signifyd provides chargeback guarantees — if they approve an order and it results in a chargeback, they reimburse you. This is the most comprehensive solution for Shopify.

1. Install Signifyd from the Shopify App Store
2. Signifyd automatically reviews every order using ML scoring
3. Orders Signifyd flags go into a review queue in the Signifyd console
4. Set up the Signifyd Shopify integration to automatically hold or cancel high-risk orders

WooCommerce

WooCommerce does not include fraud detection. You need either a payment processor with built-in fraud tools or a dedicated plugin.

Option A: Stripe Radar (recommended if using Stripe for WooCommerce)

If using the WooCommerce Stripe Payment Gateway:

1. Stripe Radar is automatically enabled — it scores every charge on your Stripe account
2. In the Stripe Dashboard, go to Radar → Rules to add custom blocking/review rules: # Block orders over $500 from high-fraud-rate IP countries Block if:order_amount: > 50000 and:ip_country: in ('NG', 'RO') # Review first-time customers placing large orders Review if:order_amount: > 20000 and:customer_account_age: < 7 # Block cards used more than 3 times in the last hour Block if:card_velocity_hour: > 3
3. Orders flagged for review appear in Stripe Dashboard → Radar → Reviews

Option B: WooCommerce Anti-Fraud plugin (free)

1. Install WooCommerce Anti-Fraud from the plugin directory
2. Configure risk scoring rules based on:

- Order amount thresholds - New customer + high value combination - Proxy/VPN IP detection - Billing/shipping country mismatch

1. High-risk orders are placed in "On Hold" status for manual review

Option C: Kount or NoFraud (enterprise) For high-volume WooCommerce stores, enterprise fraud prevention platforms offer:

• Kount: full fraud management platform with ML scoring, manual review tools, and chargeback management
• NoFraud: provides a fraud protection guarantee similar to Signifyd; integrates via WooCommerce plugin

BigCommerce

Signifyd for BigCommerce:

1. Install the Signifyd app from the BigCommerce App Marketplace
2. Configure automatic hold or cancellation of high-risk orders
3. Signifyd's guarantee covers chargebacks on approved orders

Payment processor fraud tools:

• Stripe (via BigCommerce Stripe integration): Radar is included; configure rules in the Stripe Dashboard
• PayPal: PayPal's fraud management filters are available in your PayPal business account settings
• Braintree: Advanced fraud protection via Kount is available as an add-on

Custom / Headless

For custom storefronts using Stripe, leverage Stripe Radar for ML scoring and add application-layer velocity checks for business-specific patterns.

Retrieve Stripe's fraud score after payment attempt:

const paymentIntent = await stripe.paymentIntents.retrieve(paymentIntentId, {
  expand: ['latest_charge'],
});
const riskScore = paymentIntent.latest_charge.outcome?.risk_score;   // 0–100
const riskLevel = paymentIntent.latest_charge.outcome?.risk_level;   // 'normal', 'elevated', 'highest'

Request 3D Secure for high-risk transactions (shifts chargeback liability to card issuer):

const paymentIntent = await stripe.paymentIntents.create({
  amount: order.totalCents,
  currency: 'usd',
  payment_method_options: {
    card: {
      // 'automatic' = Stripe decides; 'challenge' = always require 3DS for high-risk
      request_three_d_secure: riskScore > 70 ? 'challenge' : 'automatic',
    },
  },
});

Application-layer velocity checks:

import Redis from 'ioredis';
const redis = new Redis(process.env.REDIS_URL!);

async function checkVelocity(params: { email: string; ip: string; cardFingerprint: string; amountCents: number }) {
  const { email, ip, cardFingerprint, amountCents } = params;

  // IP: max 10 orders per hour
  const ipCount = await redis.incr(`vel:ip:${ip}`);
  if (ipCount === 1) await redis.expire(`vel:ip:${ip}`, 3600);
  if (ipCount > 10) return { allowed: false, reason: 'ip_velocity' };

  // Email: max 5 orders per 24 hours
  const emailCount = await redis.incr(`vel:email:${email.toLowerCase()}`);
  if (emailCount === 1) await redis.expire(`vel:email:${email.toLowerCase()}`, 86400);
  if (emailCount > 5) return { allowed: false, reason: 'email_velocity' };

  // Card: max $500 per day
  const spendKey = `vel:spend:${cardFingerprint}`;
  const currentSpend = parseInt(await redis.get(spendKey) ?? '0');
  if (currentSpend + amountCents > 50000) return { allowed: false, reason: 'daily_spend_limit' };

  return { allowed: true };
}

Manual review queue:

async function flagForManualReview(orderId: string, riskScore: number, signals: Record<string, unknown>) {
  // Hold the order — do NOT fulfill; do NOT capture payment (authorize only)
  await db.orders.update(orderId, {
    status: 'pending_fraud_review',
    fraud_risk_score: riskScore,
    fraud_signals: signals,
    review_requested_at: new Date(),
  });

  // Notify fraud review team
  await sendSlackAlert('#fraud-review', {
    text: `Order ${orderId} flagged for review. Risk score: ${riskScore}/100`,
    actions: [
      { text: 'Approve', url: `${ADMIN_URL}/fraud-review/${orderId}/approve` },
      { text: Reject', url: `${ADMIN_URL}/fraud-review/${orderId}/reject` },
    ],
  });
}

// Auto-cancel unreviewed orders after 48 hours
async function expireUnreviewedOrders() {
  const expired = await db.orders.findExpiredReviews(48);
  for (const order of expired) {
    await stripe.paymentIntents.cancel(order.payment_intent_id);
    await db.orders.update(order.id, { status: 'fraud_review_expired' });
    await sendOrderCancellationEmail(order);
  }
}

Best Practices

• Layer defenses — no single signal reliably stops all fraud; combine Stripe Radar, velocity checks, IP reputation, and device fingerprinting
• Use authorize-then-capture for high-risk orders — authorize at checkout to hold funds, then capture only after fraud review passes; releasing an authorization is less costly than issuing a refund
• Track false positive rate as a KPI — if more than 1% of legitimate orders are blocked or held, your rules are too aggressive; measure both fraud losses and revenue lost to false positives
• Rotate and obfuscate fraud rules — sophisticated fraudsters probe checkout flows to find rule thresholds; never expose block reasons in API error messages
• Keep a deny-list of fraudulent emails, cards, and devices — once fraud is confirmed via chargeback, add the identifiers to a blocklist for future orders
• Review your chargeback rate monthly — if it climbs above 0.5% for Visa/Mastercard, review your fraud rules; exceeding 0.9% triggers Visa's dispute monitoring program

Common Pitfalls

Related Skills

• @secure-checkout
• @account-security
• @stripe-integration
• @bot-protection
• @gdpr-ecommerce