SIM Swap Fraud Detection:
How Phone Authentication Prevents $26K Average Losses

// SIM Swap Detection with Phone Authentication API
async function detectSimSwap(phoneNumber, userId) {
  try {
    // Step 1: Check carrier and account status
    const phoneCheck = await fetch('https://api.phone-check.app/v1/validate', {
      method: 'POST',
      headers: {
        'Authorization': 'Bearer YOUR_API_KEY',
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({
        phone_number: phoneNumber,
        include_carrier: true,
        include_porting_history: true,
        include_subscriber_status: true
      })
    });

    const result = await phoneCheck.json();

    // Step 2: Analyze risk signals
    const riskSignals = {
      recentCarrierChange: result.carrier.ported_within_72h,
      accountSuspicious: result.subscriber.status !== 'active',
      simMismatch: result.sim.iccid !== user.stored_iccid,
      locationAnomaly: detectLocationAnomaly(result.network)
    };

    // Step 3: Calculate risk score
    const riskScore = calculateRiskScore(riskSignals);

    // Step 4: Take action based on risk
    if (riskScore >= 80) {
      // High risk: Block and alert security team
      return {
        allowed: false,
        reason: 'SIM swap detected',
        action: 'block',
        requires: ['in_person_verification', 'id_document']
      };
    } else if (riskScore >= 50) {
      // Medium risk: Require additional verification
      return {
        allowed: false,
        reason: 'Suspicious activity detected',
        action: 'step_up_auth',
        requires: ['hardware_key', 'biometric', 'security_questions']
      };
    }

    // Low risk: Proceed normally
    return {
      allowed: true,
      risk_score: riskScore,
      carrier: result.carrier.name
    };

  } catch (error) {
    console.error('SIM swap detection failed:', error);
    // Fail securely: Require additional verification
    return {
      allowed: false,
      reason: 'Verification unavailable',
      action: 'step_up_auth'
    };
  }
}

// Risk scoring algorithm
function calculateRiskScore(signals) {
  let score = 0;

  if (signals.recentCarrierChange) score += 40;
  if (signals.accountSuspicious) score += 30;
  if (signals.simMismatch) score += 35;
  if (signals.locationAnomaly) score += 25;

  return Math.min(score, 100);
}