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Security and Compliance Hardening - Implementation Summary

Issue: H. Security and Compliance Hardening (Issues 71-80)

Problem Statement

High-risk fraud actions should leave a complete, searchable audit trail with clear lockout semantics. Improve lockout logging and admin visibility.

Implementation Date

April 25, 2026

Changes Implemented

1. Audit Action Types Enhancement

File: src/audit/entities/audit-log.entity.ts

Added three new audit action types for fraud-related events:

  • FRAUD_ALERT: Logged when a fraud alert is created
  • FRAUD_LOCKOUT: Logged when an account is automatically locked due to fraud
  • FRAUD_REVIEW: Logged when an admin reviews a fraud alert

2. FraudAlert Entity Enhancement

File: src/fraud/entities/fraud-alert.entity.ts

Added comprehensive tracking fields:

  • lockoutReason: Text field explaining why account was locked
  • lockoutTimestamp: When the lockout occurred
  • lockoutDurationMinutes: Expected or actual lockout duration
  • reviewedBy: Admin ID who reviewed the alert
  • reviewedAt: Timestamp of review
  • reviewNotes: Admin notes during review
  • updatedAt: Automatic timestamp for last update

3. FraudService Audit Integration

File: src/fraud/fraud.service.ts

Dependencies Added:

  • AuditService: For direct audit logging
  • EventEmitter2: For emitting fraud events

Audit Events Emitted:

  1. fraud.alert_created (Line ~99-127)

    • Emitted when any fraud alert is created (score >= 20)
    • Includes: userId, riskScore, status, ipAddress, triggeredRules
    • Full state tracking with previous/new values

  2. fraud.account_locked (Line ~131-153)

    • Emitted when automated lockout is triggered (3+ flags in 60 minutes)
    • Includes: userId, fraudAlertId, flagCount, riskScore, lockoutReason
    • Tracks user status change (e.g., ACTIVE → LOCKED)

Key Features:

  • All fraud alerts now create immutable audit logs
  • Lockout events include complete context (triggered rules, flag count, IP)
  • State diffs recorded for compliance requirements

4. Fraud Module Dependencies

File: src/fraud/fraud.module.ts

Added required module imports:

  • AuditModule: For audit service integration
  • EventEmitterModule.forRoot(): For event emission

5. Audit Event Listeners

File: src/audit/audit.listener.ts

Added three new event handlers:

  1. handleFraudAlertCreated() (Line ~237-258)

    • Listens to: fraud.alert_created
    • Creates audit log with FRAUD_ALERT action type
    • Logs risk score and triggered rules

  2. handleFraudAccountLocked() (Line ~264-285)

    • Listens to: fraud.account_locked
    • Creates audit log with FRAUD_LOCKOUT action type
    • Status set to WARNING for visibility

  3. handleFraudAlertReviewed() (Line ~291-312)

    • Listens to: fraud.alert_reviewed
    • Creates audit log with FRAUD_REVIEW action type
    • Tracks reviewer accountability

6. Admin Fraud Controller Enhancement

File: src/admin/admin-fraud.controller.ts

New Endpoints:

  1. GET /admin/fraud/alerts (Enhanced)

    • Added pagination support (page, limit query params)
    • Added filtering by status and userId
    • Returns structured response with data and meta

  2. GET /admin/fraud/alerts/:id (New)

    • Get single fraud alert details
    • Returns complete alert object

  3. PATCH /admin/fraud/alerts/:id/review (Enhanced)

    • Now captures reviewer ID from authenticated user
    • Records review timestamp and notes
    • Emits fraud.alert_reviewed audit event
    • Full state diff tracking (previous → new status)

  4. GET /admin/fraud/alerts/:id/audit-trail (New)

    • Returns complete audit trail for a fraud alert
    • Includes both alert events and related lockout events
    • Searchable and filterable

  5. GET /admin/fraud/lockouts (New)

    • List all account lockouts with pagination
    • Filter by userId
    • Query audit logs for FRAUD_LOCKOUT events

  6. GET /admin/fraud/stats (New)

    • Fraud statistics dashboard
    • Alert counts: 24h, 7d, 30d
    • Lockout counts: 24h, 7d
    • Real-time metrics for admin visibility

Dependencies Added:

  • EventEmitter2: For emitting review events
  • AuditService: For querying audit logs and lockouts

7. Comprehensive Test Coverage

Files:

  • src/fraud/tests/fraud.service.spec.ts (Enhanced)
  • src/admin/admin-fraud.controller.spec.ts (New)

New Tests:

  1. FraudService Tests:

    • Test audit event emission on alert creation
    • Test lockout audit event emission after 3 flags
    • Verify event payload structure
    • Verify action types and metadata

  2. AdminFraudController Tests:

    • Test paginated alert listing
    • Test filtering by status and userId
    • Test alert review with audit event emission
    • Test audit trail retrieval
    • Test lockout listing
    • Test statistics endpoint

8. Documentation Updates

File: src/fraud/FRAUD_DETECTION.md

Sections Added/Updated:

  1. Overview: Added audit trail and admin visibility features
  2. Features: Added lockout protocol and audit trail features
  3. FraudAlert Entity: Documented new lockout and review tracking fields
  4. Audit Trail Integration (New Section):
    • Audit action types explained
    • Events emitted with payloads documented
    • Audit listeners documented
  5. Admin Controllers: Updated with all new endpoints
  6. Database Schema: Updated with new columns
  7. Usage Examples: Added comprehensive API examples for:
    • Paginated alert queries
    • Filtering alerts
    • Reviewing alerts with notes
    • Retrieving audit trails
    • Viewing lockouts
    • Getting statistics
    • Audit trail queries
  8. Security Notes: Enhanced with lockout semantics and audit trail details

Lockout Semantics

Automated Lockout Protocol

  1. Trigger: 3+ fraud flags within 60-minute window
  2. Action: User status changed to LOCKED
  3. Notification: Email sent to user
  4. Audit: Complete audit log created with:
    • Previous user status
    • New user status (LOCKED)
    • Fraud alert ID that triggered lockout
    • Risk score and triggered rules
    • Flag count and time window
    • Lockout reason

Admin Visibility

  • View all lockouts: GET /admin/fraud/lockouts
  • Filter by user: GET /admin/fraud/lockouts?userId=xxx
  • View audit trail: GET /admin/fraud/alerts/:id/audit-trail
  • Statistics: GET /admin/fraud/stats

Audit Trail Completeness

Every fraud action now leaves an immutable record:

Alert Creation

{
  "action": "FRAUD_ALERT",
  "userId": "user-123",
  "status": "WARNING",
  "resourceType": "fraud_alert",
  "resourceId": "alert-uuid",
  "stateNewValue": {
    "riskScore": 85,
    "status": "manual_review",
    "reason": "high_value_order, new_account"
  },
  "metadata": {
    "alertId": "alert-uuid",
    "orderId": "order-uuid",
    "triggeredRules": ["high_value_order", "new_account"],
    "ipAddress": "192.168.1.100"
  }
}

Account Lockout

{
  "action": "FRAUD_LOCKOUT",
  "userId": "user-123",
  "status": "WARNING",
  "resourceType": "user",
  "resourceId": "user-123",
  "statePreviousValue": { "status": "active" },
  "stateNewValue": { "status": "locked" },
  "metadata": {
    "fraudAlertId": "alert-uuid",
    "riskScore": 95,
    "flagCount": 3,
    "triggeredRules": ["high_value_order", "new_account", "known_bad_ip"],
    "lockoutReason": "Automated lockout after 3 fraud flags within 60 minutes"
  }
}

Admin Review

{
  "action": "FRAUD_REVIEW",
  "userId": "admin-456",
  "status": "SUCCESS",
  "resourceType": "fraud_alert",
  "resourceId": "alert-uuid",
  "statePreviousValue": { "status": "pending" },
  "stateNewValue": { "status": "safe", "notes": "False positive - verified" },
  "metadata": {
    "alertId": "alert-uuid",
    "userId": "user-123",
    "riskScore": 85,
    "previousStatus": "pending",
    "newStatus": "safe",
    "reviewer": "admin-456"
  }
}

Search and Query Capabilities

Admins can now search audit logs with:

# By action type
GET /admin/audit?action=FRAUD_ALERT

# By user
GET /admin/audit?userId=user-123

# By date range
GET /admin/audit?startDate=2026-04-01&endDate=2026-04-25

# By resource
GET /admin/audit?resourceType=fraud_alert&resourceId=alert-uuid

# Combined filters
GET /admin/audit?action=FRAUD_LOCKOUT&startDate=2026-04-01

Testing

Run Fraud Tests

npm test -- src/fraud/tests/fraud.service.spec.ts
npm test -- src/admin/admin-fraud.controller.spec.ts

Test Coverage

  • ✅ Alert creation with audit emission
  • ✅ Lockout trigger with audit emission
  • ✅ Admin review with audit emission
  • ✅ Audit trail retrieval
  • ✅ Lockout listing and filtering
  • ✅ Statistics calculation
  • ✅ Pagination and filtering

Migration Required

After deploying these changes, run a database migration to add new columns to fraud_alerts table:

ALTER TABLE fraud_alerts
ADD COLUMN IF NOT EXISTS "lockoutReason" TEXT,
ADD COLUMN IF NOT EXISTS "lockoutTimestamp" TIMESTAMP,
ADD COLUMN IF NOT EXISTS "lockoutDurationMinutes" INT,
ADD COLUMN IF NOT EXISTS "reviewedBy" VARCHAR,
ADD COLUMN IF NOT EXISTS "reviewedAt" TIMESTAMP,
ADD COLUMN IF NOT EXISTS "reviewNotes" TEXT,
ADD COLUMN IF NOT EXISTS "updatedAt" TIMESTAMP DEFAULT NOW();

Backward Compatibility

✅ No Breaking Changes:

  • All existing endpoints continue to work
  • New fields are nullable
  • Audit events are additive (don't replace existing logging)
  • Existing fraud alerts will work without new fields

Security and Compliance Benefits

  1. Complete Audit Trail: Every fraud action is logged immutably
  2. Searchable Logs: Admins can query by user, date, action type, resource
  3. Lockout Transparency: Clear visibility into why/when accounts were locked
  4. Review Accountability: All admin reviews tracked with ID and timestamp
  5. State Tracking: Previous and new states recorded for all actions
  6. Compliance Ready: Meets requirements for financial fraud audit trails
  7. Real-time Monitoring: Statistics dashboard for proactive monitoring
  8. Event-Driven Architecture: Decoupled audit logging via event emission

Files Modified

  1. src/audit/entities/audit-log.entity.ts - Added fraud action types
  2. src/fraud/entities/fraud-alert.entity.ts - Enhanced with tracking fields
  3. src/fraud/fraud.service.ts - Integrated audit logging
  4. src/fraud/fraud.module.ts - Added module dependencies
  5. src/audit/audit.listener.ts - Added fraud event handlers
  6. src/admin/admin-fraud.controller.ts - Enhanced with audit endpoints
  7. src/fraud/tests/fraud.service.spec.ts - Added audit tests
  8. src/admin/admin-fraud.controller.spec.ts - New test file
  9. src/fraud/FRAUD_DETECTION.md - Comprehensive documentation update

Done Criteria ✅

  • ✅ Implementation updates complete
  • ✅ Module dependencies aligned
  • ✅ Documentation updated
  • ✅ Tests added for affected areas
  • ✅ No regressions introduced (backward compatible)
  • ✅ Audit trail complete and searchable
  • ✅ Lockout semantics clearly defined
  • ✅ Admin visibility enhanced

Next Steps (Optional Enhancements)

  1. Create TypeORM migration file for new columns
  2. Add unit tests for audit listener fraud handlers
  3. Add integration tests for end-to-end audit trail
  4. Consider adding webhook notifications for lockouts
  5. Add export functionality for audit reports (CSV/PDF)
  6. Implement role-based audit log access (super-admin vs admin)