# Security Documentation - AI Study Assistant

## 🔒 COMPREHENSIVE SECURITY FRAMEWORK

---

## 📋 OVERVIEW

This document outlines the complete security architecture, policies, and procedures for the AI Study Assistant platform, ensuring data protection, privacy compliance, and secure operations across all components.

---

## 🛡️ SECURITY ARCHITECTURE

### Defense in Depth Strategy

#### Multi-Layer Security
```
┌─────────────────────────────────────────────────────┐
│                    APPLICATION LAYER                    │
│  • Input Validation • Authentication • Authorization   │
├─────────────────────────────────────────────────────┤
│                     API LAYER                         │
│  • Rate Limiting • API Security • Request Validation │
├─────────────────────────────────────────────────────┤
│                    DATA LAYER                         │
│  • Encryption • Access Control • Audit Logging      │
├─────────────────────────────────────────────────────┤
│                 INFRASTRUCTURE LAYER                   │
│  • Network Security • Container Security • Monitoring│
└─────────────────────────────────────────────────────┘
```

#### Security Domains
- **Application Security**: Code-level protections
- **Data Security**: Encryption and access control
- **Network Security**: Communication protection
- **Infrastructure Security**: Platform protection
- **Operational Security**: Processes and procedures

---

## 🔐 AUTHENTICATION & AUTHORIZATION

### Authentication Framework

#### Firebase Authentication
```typescript
// Authentication configuration
const authConfig = {
  providers: [
    'email',           // Email/password
    'google',          // Google OAuth
    'apple',           // Apple Sign In (iOS)
  ],
  passwordPolicy: {
    minLength: 8,
    requireUppercase: false,
    requireLowercase: false,
    requireNumbers: false,
    requireSpecialChars: false,
  },
  sessionManagement: {
    maxAge: 30 * 60 * 1000,  // 30 minutes
    refreshThreshold: 5 * 60 * 1000,  // 5 minutes
  },
  multiFactorAuth: {
    enabled: false,  // Future enhancement
    methods: ['sms', 'totp'],
  }
};
```

#### Token Management
```typescript
// JWT Token validation
export class TokenValidator {
  async validateToken(token: string): Promise<AuthResult> {
    try {
      const decodedToken = await admin.auth().verifyIdToken(token);
      
      // Check token age
      const now = Date.now() / 1000;
      if (decodedToken.exp < now) {
        throw new Error('Token expired');
      }
      
      // Check user status
      const user = await this.getUser(decodedToken.uid);
      if (!user.isActive) {
        throw new Error('User account disabled');
      }
      
      return {
        success: true,
        user: decodedToken,
        permissions: await this.getPermissions(decodedToken.uid),
      };
    } catch (error) {
      return {
        success: false,
        error: error.message,
      };
    }
  }
}
```

### Authorization Framework

#### Role-Based Access Control (RBAC)
```typescript
// Role definitions
export enum UserRole {
  STUDENT = 'student',
  TEACHER = 'teacher',
  ADMIN = 'admin',
  SUPER_ADMIN = 'super_admin',
}

// Permission definitions
export enum Permission {
  // Student permissions
  READ_OWN_CONTENT = 'read_own_content',
  SUBMIT_QUIZZES = 'submit_quizzes',
  ASK_QUESTIONS = 'ask_questions',
  VIEW_OWN_PROGRESS = 'view_own_progress',
  
  // Teacher permissions
  MANAGE_CLASS = 'manage_class',
  UPLOAD_CONTENT = 'upload_content',
  CREATE_QUIZZES = 'create_quizzes',
  VIEW_STUDENT_PROGRESS = 'view_student_progress',
  
  // Admin permissions
  MANAGE_USERS = 'manage_users',
  MANAGE_SCHOOLS = 'manage_schools',
  VIEW_ANALYTICS = 'view_analytics',
  MANAGE_SYSTEM = 'manage_system',
}

// Role-Permission mapping
const rolePermissions = {
  [UserRole.STUDENT]: [
    Permission.READ_OWN_CONTENT,
    Permission.SUBMIT_QUIZZES,
    Permission.ASK_QUESTIONS,
    Permission.VIEW_OWN_PROGRESS,
  ],
  [UserRole.TEACHER]: [
    ...rolePermissions[UserRole.STUDENT],
    Permission.MANAGE_CLASS,
    Permission.UPLOAD_CONTENT,
    Permission.CREATE_QUIZZES,
    Permission.VIEW_STUDENT_PROGRESS,
  ],
  [UserRole.ADMIN]: [
    ...rolePermissions[UserRole.TEACHER],
    Permission.MANAGE_USERS,
    Permission.MANAGE_SCHOOLS,
    Permission.VIEW_ANALYTICS,
  ],
  [UserRole.SUPER_ADMIN]: [
    ...rolePermissions[UserRole.ADMIN],
    Permission.MANAGE_SYSTEM,
  ],
};
```

#### Authorization Middleware
```typescript
// Express middleware for authorization
export const authorize = (requiredPermission: Permission) => {
  return async (req: Request, res: Response, next: NextFunction) => {
    try {
      const token = req.headers.authorization?.split('Bearer ')[1];
      if (!token) {
        return res.status(401).json({ error: 'Authentication required' });
      }
      
      const authResult = await tokenValidator.validateToken(token);
      if (!authResult.success) {
        return res.status(401).json({ error: authResult.error });
      }
      
      const userPermissions = authResult.permissions;
      if (!userPermissions.includes(requiredPermission)) {
        return res.status(403).json({ error: 'Insufficient permissions' });
      }
      
      req.user = authResult.user;
      req.permissions = userPermissions;
      next();
    } catch (error) {
      res.status(500).json({ error: 'Authorization error' });
    }
  };
};
```

---

## 🔒 DATA PROTECTION

### Encryption Standards

#### Data-at-Rest Encryption
```typescript
// Firebase Firestore encryption
const encryptionConfig = {
  // Default Firebase encryption
  firestore: {
    encryption: 'AES-256',
    keyRotation: '90 days',
  },
  
  // Additional encryption for sensitive data
  sensitiveFields: [
    'email',
    'personalInfo',
    'healthData',
    'assessmentResults',
  ],
  
  // Custom encryption for PII
  piiEncryption: {
    algorithm: 'AES-256-GCM',
    keyDerivation: 'PBKDF2',
    iterations: 100000,
  },
};
```

#### Data-in-Transit Encryption
```typescript
// HTTPS/TLS configuration
const tlsConfig = {
  version: 'TLS 1.3',
  ciphers: [
    'TLS_AES_256_GCM_SHA384',
    'TLS_CHACHA20_POLY1305_SHA256',
    'TLS_AES_128_GCM_SHA256',
  ],
  certificates: {
    provider: 'Let\'s Encrypt',
    autoRenewal: true,
    monitoring: true,
  },
};
```

#### Field-Level Encryption
```typescript
// Sensitive data encryption
export class FieldEncryption {
  private readonly algorithm = 'aes-256-gcm';
  private readonly keyLength = 32;
  
  async encryptField(data: string, key: string): Promise<EncryptedData> {
    const iv = crypto.randomBytes(16);
    const cipher = crypto.createCipher(this.algorithm, key);
    cipher.setAAD(Buffer.from('teachit-field', 'utf8'));
    
    let encrypted = cipher.update(data, 'utf8', 'hex');
    encrypted += cipher.final('hex');
    
    const tag = cipher.getAuthTag();
    
    return {
      data: encrypted,
      iv: iv.toString('hex'),
      tag: tag.toString('hex'),
    };
  }
  
  async decryptField(encryptedData: EncryptedData, key: string): Promise<string> {
    const decipher = crypto.createDecipher(this.algorithm, key);
    decipher.setAAD(Buffer.from('teachit-field', 'utf8'));
    decipher.setAuthTag(Buffer.from(encryptedData.tag, 'hex'));
    
    let decrypted = decipher.update(encryptedData.data, 'hex', 'utf8');
    decrypted += decipher.final('utf8');
    
    return decrypted;
  }
}
```

### Data Classification

#### Data Sensitivity Levels
```typescript
export enum DataClassification {
  PUBLIC = 'public',           // Public information
  INTERNAL = 'internal',       // Internal use only
  CONFIDENTIAL = 'confidential', // Sensitive business data
  RESTRICTED = 'restricted',    // Highly sensitive data
}

// Data classification mapping
const dataClassification = {
  // Public data
  'appVersion': DataClassification.PUBLIC,
  'featureFlags': DataClassification.PUBLIC,
  
  // Internal data
  'userPreferences': DataClassification.INTERNAL,
  'learningProgress': DataClassification.INTERNAL,
  'quizResults': DataClassification.INTERNAL,
  
  // Confidential data
  'email': DataClassification.CONFIDENTIAL,
  'personalInfo': DataClassification.CONFIDENTIAL,
  'schoolData': DataClassification.CONFIDENTIAL,
  
  // Restricted data
  'assessmentScores': DataClassification.RESTRICTED,
  'behavioralData': DataClassification.RESTRICTED,
  'healthInformation': DataClassification.RESTRICTED,
};
```

#### Data Retention Policy
```typescript
// Data retention configuration
const retentionPolicy = {
  // User data
  userData: {
    active: 'indefinite',                    // While account is active
    inactive: '2 years',                      // After account closure
    deleted: '30 days',                       // After deletion request
  },
  
  // Learning data
  learningProgress: {
    detailed: '2 years',                      // Detailed progress
    summary: '7 years',                       // Summary statistics
    aggregated: 'indefinite',                 // Aggregated analytics
  },
  
  // System logs
  logs: {
    access: '90 days',                        // Access logs
    errors: '1 year',                        // Error logs
    performance: '30 days',                   // Performance logs
    security: '7 years',                     // Security logs
  },
  
  // Audit data
  audit: {
    userActions: '7 years',                   // User action logs
    adminActions: 'indefinite',               // Admin actions
    dataAccess: '7 years',                    // Data access logs
  },
};
```

---

## 🌐 NETWORK SECURITY

### API Security

#### Rate Limiting
```typescript
// Rate limiting configuration
export const rateLimitConfig = {
  // Global limits
  global: {
    windowMs: 60 * 1000,                    // 1 minute
    max: 1000,                               // 1000 requests per minute
  },
  
  // Per-endpoint limits
  endpoints: {
    '/auth/signin': {
      windowMs: 15 * 60 * 1000,              // 15 minutes
      max: 5,                                // 5 login attempts
    },
    '/tutor/ask': {
      windowMs: 60 * 1000,                   // 1 minute
      max: 20,                               // 20 questions per minute
    },
    '/quiz/submit': {
      windowMs: 60 * 1000,                   // 1 minute
      max: 10,                               // 10 quiz submissions per minute
    },
    '/content/upload': {
      windowMs: 60 * 1000,                   // 1 minute
      max: 5,                                // 5 uploads per minute
    },
  },
  
  // Per-user limits
  perUser: {
    windowMs: 60 * 1000,                     // 1 minute
    max: 100,                               // 100 requests per minute per user
  },
};
```

#### API Security Headers
```typescript
// Security headers middleware
export const securityHeaders = {
  'Content-Security-Policy': [
    "default-src 'self'",
    "script-src 'self' 'unsafe-inline'",
    "style-src 'self' 'unsafe-inline'",
    "img-src 'self' data: https:",
    "font-src 'self'",
    "connect-src 'self' https://api.teachit.app",
    "frame-ancestors 'none'",
    "base-uri 'self'",
    "form-action 'self'",
  ].join('; '),
  
  'X-Content-Type-Options': 'nosniff',
  'X-Frame-Options': 'DENY',
  'X-XSS-Protection': '1; mode=block',
  'Strict-Transport-Security': 'max-age=31536000; includeSubDomains',
  'Referrer-Policy': 'strict-origin-when-cross-origin',
  'Permissions-Policy': 'camera=(), microphone=(), geolocation=()',
};
```

#### Input Validation
```typescript
// Input validation middleware
export const validateInput = (schema: Joi.Schema) => {
  return (req: Request, res: Response, next: NextFunction) => {
    const { error } = schema.validate(req.body);
    if (error) {
      return res.status(400).json({
        error: 'Validation error',
        details: error.details.map(d => d.message),
      });
    }
    next();
  };
};

// Example validation schemas
export const schemas = {
  askTutor: Joi.object({
    query: Joi.string().min(5).max(500).required(),
    mode: Joi.string().valid('EXPLANATION', 'TUTOR', 'EXPLORATION', 'REMEDIAL').required(),
    context: Joi.object({
      subject: Joi.string(),
      currentTopic: Joi.string(),
    }).optional(),
  }),
  
  submitQuiz: Joi.object({
    quizId: Joi.string().required(),
    answers: Joi.array().items(
      Joi.object({
        questionId: Joi.string().required(),
        answer: Joi.alternatives().try(
          Joi.number(),
          Joi.string(),
          Joi.array()
        ).required(),
        timeSpent: Joi.number().min(0).max(3600).optional(),
      })
    ).required(),
  }),
};
```

### Database Security

#### Firestore Security Rules
```javascript
// Enhanced security rules
rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    
    // Helper functions
    function isAuthenticated() {
      return request.auth != null;
    }
    
    function isSameSchool(schoolId) {
      return isAuthenticated() && 
             get(/databases/$(database)/documents/users/$(request.auth.uid)).data.schoolId == schoolId;
    }
    
    function hasRole(role) {
      return isAuthenticated() && 
             get(/databases/$(database)/documents/users/$(request.auth.uid)).data.role == role;
    }
    
    function isDataOwner(userId) {
      return isAuthenticated() && request.auth.uid == userId;
    }
    
    function isValidTimestamp() {
      return request.time == request.time;
    }
    
    function hasValidFields(fields) {
      return request.resource.data.keys().hasAll(fields);
    }
    
    // Users collection
    match /users/{userId} {
      allow read, write: if isDataOwner(userId) || hasRole('admin');
      allow create: if isAuthenticated() && 
                     isDataOwner(userId) &&
                     hasValidFields(['email', 'role', 'schoolId']) &&
                     isValidTimestamp();
      allow update: if isDataOwner(userId) || hasRole('admin');
      allow delete: if hasRole('admin');
    }
    
    // Learning states
    match /learningStates/{studentId} {
      allow read: if isAuthenticated() && 
                     (isDataOwner(studentId) || isSameSchool(resource.data.schoolId));
      allow write: if isAuthenticated() && 
                     (isDataOwner(studentId) || hasRole('teacher'));
      allow create: if isAuthenticated() && isDataOwner(studentId);
      allow update: if isAuthenticated() && 
                     (isDataOwner(studentId) || hasRole('teacher'));
      allow delete: if hasRole('admin');
    }
    
    // Content chunks
    match /contentChunks/{chunkId} {
      allow read: if isAuthenticated() && isSameSchool(resource.data.schoolId);
      allow write: if isAuthenticated() && 
                     (hasRole('teacher') || hasRole('admin')) &&
                     isSameSchool(resource.data.schoolId);
      allow create: if isAuthenticated() && 
                     hasRole('teacher') &&
                     isSameSchool(request.resource.data.schoolId);
      allow update: if isAuthenticated() && 
                     (hasRole('teacher') || hasRole('admin')) &&
                     isSameSchool(resource.data.schoolId);
      allow delete: if isAuthenticated() && 
                     (hasRole('teacher') || hasRole('admin')) &&
                     isSameSchool(resource.data.schoolId);
    }
    
    // Quiz attempts
    match /quizAttempts/{attemptId} {
      allow read: if isAuthenticated() && 
                     (isDataOwner(resource.data.studentId) || isSameSchool(resource.data.schoolId));
      allow write: if isAuthenticated() && 
                     (isDataOwner(resource.data.studentId) || hasRole('teacher'));
      allow create: if isAuthenticated() && isDataOwner(resource.data.studentId);
      allow update: if hasRole('admin');
      allow delete: if hasRole('admin');
    }
    
    // Audit logs (admin only)
    match /auditLogs/{logId} {
      allow read, write, create: if hasRole('admin');
    }
  }
}
```

#### Storage Security Rules
```javascript
// Firebase Storage security rules
rules_version = '2';
service firebase.storage {
  match /b/{bucket}/o {
    
    // Helper functions
    function isAuthenticated() {
      return request.auth != null;
    }
    
    function isSameSchool(schoolId) {
      return isAuthenticated() && 
             get(/databases/(default)/documents/users/$(request.auth.uid)).data.schoolId == schoolId;
    }
    
    function hasRole(role) {
      return isAuthenticated() && 
             get(/databases/(default)/documents/users/$(request.auth.uid)).data.role == role;
    }
    
    // Content files
    match /content/{schoolId}/{allPaths=**} {
      allow read: if isAuthenticated() && isSameSchool(schoolId);
      allow write: if isAuthenticated() && 
                     (hasRole('teacher') || hasRole('admin')) &&
                     isSameSchool(schoolId);
      allow create: if isAuthenticated() && 
                     (hasRole('teacher') || hasRole('admin')) &&
                     isSameSchool(schoolId) &&
                     request.resource.size < 50 * 1024 * 1024; // 50MB limit
    }
    
    // User avatars
    match /avatars/{userId}/{fileName} {
      allow read: if isAuthenticated();
      allow write: if isAuthenticated() && 
                     request.auth.uid == userId &&
                     request.resource.size < 5 * 1024 * 1024; // 5MB limit
      allow delete: if isAuthenticated() && request.auth.uid == userId;
    }
    
    // Temporary files
    match /temp/{userId}/{fileName} {
      allow read: if isAuthenticated() && request.auth.uid == userId;
      allow write: if isAuthenticated() && 
                     request.auth.uid == userId &&
                     request.resource.size < 10 * 1024 * 1024; // 10MB limit
      allow delete: if isAuthenticated() && request.auth.uid == userId;
    }
  }
}
```

---

## 🔍 MONITORING & AUDITING

### Security Monitoring

#### Real-time Monitoring
```typescript
// Security monitoring service
export class SecurityMonitor {
  private alerts: SecurityAlert[] = [];
  
  async detectAnomalies(request: Request): Promise<SecurityAlert[]> {
    const alerts: SecurityAlert[] = [];
    
    // Rate limit detection
    const rateLimitAlert = await this.checkRateLimit(request);
    if (rateLimitAlert) alerts.push(rateLimitAlert);
    
    // Suspicious activity detection
    const suspiciousAlert = await this.checkSuspiciousActivity(request);
    if (suspiciousAlert) alerts.push(suspiciousAlert);
    
    // Geolocation anomaly detection
    const geoAlert = await this.checkGeolocationAnomaly(request);
    if (geoAlert) alerts.push(geoAlert);
    
    return alerts;
  }
  
  private async checkRateLimit(request: Request): Promise<SecurityAlert | null> {
    const key = `rate_limit:${request.ip}:${request.path}`;
    const count = await this.redis.incr(key);
    
    if (count === 1) {
      await this.redis.expire(key, 60); // 1 minute window
    }
    
    if (count > 100) {
      return {
        type: 'RATE_LIMIT_EXCEEDED',
        severity: 'HIGH',
        message: `Rate limit exceeded for ${request.ip}`,
        metadata: {
          ip: request.ip,
          path: request.path,
          count: count,
        },
      };
    }
    
    return null;
  }
  
  private async checkSuspiciousActivity(request: Request): Promise<SecurityAlert | null> {
    // Check for unusual patterns
    const patterns = [
      /union.*select/i,           // SQL injection
      /<script.*>/i,             // XSS
      /\.\.\//,                   // Path traversal
      /javascript:/i,            // JavaScript injection
    ];
    
    const body = JSON.stringify(request.body);
    const query = request.url;
    
    for (const pattern of patterns) {
      if (pattern.test(body) || pattern.test(query)) {
        return {
          type: 'SUSPICIOUS_PATTERN',
          severity: 'MEDIUM',
          message: `Suspicious pattern detected: ${pattern}`,
          metadata: {
            pattern: pattern.toString(),
            ip: request.ip,
            userAgent: request.headers['user-agent'],
          },
        };
      }
    }
    
    return null;
  }
}
```

#### Audit Logging
```typescript
// Audit logging service
export class AuditLogger {
  async logSecurityEvent(event: SecurityEvent): Promise<void> {
    const auditLog = {
      timestamp: new Date().toISOString(),
      eventType: event.type,
      severity: event.severity,
      userId: event.userId,
      ipAddress: event.ipAddress,
      userAgent: event.userAgent,
      action: event.action,
      resource: event.resource,
      result: event.result,
      metadata: event.metadata,
    };
    
    // Log to Firestore
    await admin.firestore().collection('auditLogs').add(auditLog);
    
    // Log to external security system
    await this.sendToSecuritySystem(auditLog);
    
    // Check for immediate alerts
    if (event.severity === 'HIGH' || event.severity === 'CRITICAL') {
      await this.triggerSecurityAlert(auditLog);
    }
  }
  
  private async sendToSecuritySystem(log: any): Promise<void> {
    // Integration with SIEM or security monitoring system
    const securityWebhook = process.env.SECURITY_WEBHOOK_URL;
    if (securityWebhook) {
      await fetch(securityWebhook, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(log),
      });
    }
  }
  
  private async triggerSecurityAlert(log: any): Promise<void> {
    // Send immediate notification to security team
    const alert = {
      type: 'SECURITY_ALERT',
      severity: log.severity,
      message: `Security event: ${log.eventType}`,
      details: log,
    };
    
    // Send to Slack/email/SMS
    await this.sendAlert(alert);
  }
}
```

### Compliance Monitoring

#### GDPR Compliance
```typescript
// GDPR compliance monitoring
export class GDPRMonitor {
  async checkCompliance(userId: string): Promise<ComplianceReport> {
    const report: ComplianceReport = {
      userId,
      timestamp: new Date().toISOString(),
      checks: [],
      compliant: true,
    };
    
    // Check data consent
    const consentCheck = await this.checkDataConsent(userId);
    report.checks.push(consentCheck);
    
    // Check data retention
    const retentionCheck = await this.checkDataRetention(userId);
    report.checks.push(retentionCheck);
    
    // Check data processing
    const processingCheck = await this.checkDataProcessing(userId);
    report.checks.push(processingCheck);
    
    // Check data sharing
    const sharingCheck = await this.checkDataSharing(userId);
    report.checks.push(sharingCheck);
    
    report.compliant = report.checks.every(check => check.compliant);
    
    return report;
  }
  
  private async checkDataConsent(userId: string): Promise<ComplianceCheck> {
    const user = await this.getUser(userId);
    const hasConsent = user.dataConsent?.given;
    const consentUpToDate = this.isConsentRecent(user.dataConsent?.timestamp);
    
    return {
      type: 'DATA_CONSENT',
      compliant: hasConsent && consentUpToDate,
      details: {
        hasConsent,
        consentDate: user.dataConsent?.timestamp,
        consentUpToDate,
      },
    };
  }
  
  private async checkDataRetention(userId: string): Promise<ComplianceCheck> {
    const userData = await this.getUserData(userId);
    const oldData = userData.filter(data => this.isDataTooOld(data.timestamp));
    
    return {
      type: 'DATA_RETENTION',
      compliant: oldData.length === 0,
      details: {
        dataCount: userData.length,
        oldDataCount: oldData.length,
        retentionPolicy: '2 years',
      },
    };
  }
}
```

---

## 🚨 INCIDENT RESPONSE

### Incident Response Plan

#### Incident Classification
```typescript
export enum IncidentSeverity {
  LOW = 'low',           // Minor issue, limited impact
  MEDIUM = 'medium',     // Moderate issue, some impact
  HIGH = 'high',         // Serious issue, significant impact
  CRITICAL = 'critical', // Critical issue, severe impact
}

export enum IncidentType {
  DATA_BREACH = 'data_breach',
  UNAUTHORIZED_ACCESS = 'unauthorized_access',
  DENIAL_OF_SERVICE = 'denial_of_service',
  MALWARE = 'malware',
  SOCIAL_ENGINEERING = 'social_engineering',
  SYSTEM_COMPROMISE = 'system_compromise',
  PHYSICAL_SECURITY = 'physical_security',
}
```

#### Response Procedures
```typescript
// Incident response service
export class IncidentResponse {
  async handleIncident(incident: SecurityIncident): Promise<void> {
    // Step 1: Immediate response
    await this.immediateResponse(incident);
    
    // Step 2: Assessment
    const assessment = await this.assessIncident(incident);
    
    // Step 3: Containment
    await this.containIncident(incident, assessment);
    
    // Step 4: Investigation
    const investigation = await this.investigateIncident(incident);
    
    // Step 5: Recovery
    await this.recoverFromIncident(incident, investigation);
    
    // Step 6: Post-incident review
    await this.postIncidentReview(incident);
  }
  
  private async immediateResponse(incident: SecurityIncident): Promise<void> {
    // Log incident
    await this.logIncident(incident);
    
    // Alert security team
    await this.alertSecurityTeam(incident);
    
    // Initial containment if critical
    if (incident.severity === IncidentSeverity.CRITICAL) {
      await this.emergencyContainment(incident);
    }
  }
  
  private async assessIncident(incident: SecurityIncident): Promise<IncidentAssessment> {
    return {
      impact: await this.assessImpact(incident),
      scope: await this.assessScope(incident),
      urgency: this.calculateUrgency(incident),
      resources: await this.identifyResources(incident),
    };
  }
  
  private async containIncident(incident: SecurityIncident, assessment: IncidentAssessment): Promise<void> {
    switch (incident.type) {
      case IncidentType.UNAUTHORIZED_ACCESS:
        await this.containUnauthorizedAccess(incident);
        break;
      case IncidentType.DATA_BREACH:
        await this.containDataBreach(incident);
        break;
      case IncidentType.DENIAL_OF_SERVICE:
        await this.containDenialOfService(incident);
        break;
      default:
        await this.genericContainment(incident);
    }
  }
  
  private async containUnauthorizedAccess(incident: SecurityIncident): Promise<void> {
    // Revoke compromised tokens
    await this.revokeTokens(incident.userId);
    
    // Force password reset
    await this.forcePasswordReset(incident.userId);
    
    // Enable additional monitoring
    await this.enhanceMonitoring(incident.userId);
  }
  
  private async containDataBreach(incident: SecurityIncident): Promise<void> {
    // Isolate affected systems
    await this.isolateSystems(incident.affectedSystems);
    
    // Preserve evidence
    await this.preserveEvidence(incident);
    
    // Notify affected users
    await this.notifyAffectedUsers(incident);
  }
}
```

#### Communication Plan
```typescript
// Incident communication service
export class IncidentCommunication {
  async notifyStakeholders(incident: SecurityIncident): Promise<void> {
    const stakeholders = await this.getStakeholders(incident);
    
    for (const stakeholder of stakeholders) {
      await this.notifyStakeholder(stakeholder, incident);
    }
  }
  
  private async notifyStakeholder(stakeholder: Stakeholder, incident: SecurityIncident): Promise<void> {
    const message = this.createMessage(stakeholder, incident);
    
    switch (stakeholder.type) {
      case 'SECURITY_TEAM':
        await this.sendUrgentNotification(stakeholder, message);
        break;
      case 'MANAGEMENT':
        await this.sendExecutiveNotification(stakeholder, message);
        break;
      case 'LEGAL':
        await this.sendLegalNotification(stakeholder, message);
        break;
      case 'USERS':
        await this.sendUserNotification(stakeholder, message);
        break;
      case 'PUBLIC':
        await this.sendPublicNotification(stakeholder, message);
        break;
    }
  }
  
  private createMessage(stakeholder: Stakeholder, incident: SecurityIncident): string {
    const templates = {
      SECURITY_TEAM: `URGENT: ${incident.type} detected. Severity: ${incident.severity}. Immediate action required.`,
      MANAGEMENT: `Security Incident Report: ${incident.type}. Impact: ${incident.impact}. Status: ${incident.status}`,
      LEGAL: `Legal Notification: ${incident.type} incident. Potential regulatory implications.`,
      USERS: `Security Notice: We're investigating a security incident. Your account may be affected.`,
      PUBLIC: `Security Update: We're investigating a security incident and taking appropriate action.`,
    };
    
    return templates[stakeholder.type] || 'Security incident occurred.';
  }
}
```

---

## 🛡️ VULNERABILITY MANAGEMENT

### Security Testing

#### Penetration Testing
```typescript
// Penetration testing framework
export class PenetrationTest {
  async runSecurityTests(): Promise<TestResults> {
    const results: TestResults = {
      timestamp: new Date().toISOString(),
      tests: [],
      vulnerabilities: [],
      score: 0,
    };
    
    // Authentication tests
    const authTests = await this.testAuthentication();
    results.tests.push(...authTests.tests);
    results.vulnerabilities.push(...authTests.vulnerabilities);
    
    // Authorization tests
    const authzTests = await this.testAuthorization();
    results.tests.push(...authzTests.tests);
    results.vulnerabilities.push(...authzTests.vulnerabilities);
    
    // Input validation tests
    const inputTests = await this.testInputValidation();
    results.tests.push(...inputTests.tests);
    results.vulnerabilities.push(...inputTests.vulnerabilities);
    
    // Data protection tests
    const dataTests = await this.testDataProtection();
    results.tests.push(...dataTests.tests);
    results.vulnerabilities.push(...dataTests.vulnerabilities);
    
    // Calculate security score
    results.score = this.calculateSecurityScore(results);
    
    return results;
  }
  
  private async testAuthentication(): Promise<TestResult> {
    const tests = [];
    const vulnerabilities = [];
    
    // Test weak passwords
    const weakPasswordTest = await this.testWeakPasswords();
    tests.push(weakPasswordTest);
    if (weakPasswordTest.vulnerable) {
      vulnerabilities.push({
        type: 'WEAK_PASSWORDS',
        severity: 'HIGH',
        description: 'Weak password policy detected',
        recommendation: 'Implement stronger password requirements',
      });
    }
    
    // Test session management
    const sessionTest = await this.testSessionManagement();
    tests.push(sessionTest);
    if (sessionTest.vulnerable) {
      vulnerabilities.push({
        type: 'SESSION_MANAGEMENT',
        severity: 'MEDIUM',
        description: 'Session management issues detected',
        recommendation: 'Improve session security',
      });
    }
    
    return { tests, vulnerabilities };
  }
  
  private async testInputValidation(): Promise<TestResult> {
    const tests = [];
    const vulnerabilities = [];
    
    // Test SQL injection
    const sqlInjectionTest = await this.testSQLInjection();
    tests.push(sqlInjectionTest);
    if (sqlInjectionTest.vulnerable) {
      vulnerabilities.push({
        type: 'SQL_INJECTION',
        severity: 'CRITICAL',
        description: 'SQL injection vulnerability detected',
        recommendation: 'Implement proper input sanitization',
      });
    }
    
    // Test XSS
    const xssTest = await this.testXSS();
    tests.push(xssTest);
    if (xssTest.vulnerable) {
      vulnerabilities.push({
        type: 'XSS',
        severity: 'HIGH',
        description: 'Cross-site scripting vulnerability detected',
        recommendation: 'Implement proper output encoding',
      });
    }
    
    return { tests, vulnerabilities };
  }
}
```

#### Code Security Analysis
```typescript
// Static code analysis
export class CodeSecurityAnalyzer {
  async analyzeCode(codePath: string): Promise<SecurityReport> {
    const report: SecurityReport = {
      timestamp: new Date().toISOString(),
      issues: [],
      score: 0,
    };
    
    // Analyze for security issues
    const issues = await this.scanForSecurityIssues(codePath);
    report.issues = issues;
    
    // Calculate security score
    report.score = this.calculateSecurityScore(issues);
    
    return report;
  }
  
  private async scanForSecurityIssues(codePath: string): Promise<SecurityIssue[]> {
    const issues: SecurityIssue[] = [];
    
    // Scan for hardcoded secrets
    const secrets = await this.scanForSecrets(codePath);
    issues.push(...secrets);
    
    // Scan for insecure functions
    const insecureFunctions = await this.scanForInsecureFunctions(codePath);
    issues.push(...insecureFunctions);
    
    // Scan for input validation issues
    const validationIssues = await this.scanForValidationIssues(codePath);
    issues.push(...validationIssues);
    
    return issues;
  }
  
  private async scanForSecrets(codePath: string): Promise<SecurityIssue[]> {
    const secrets = [];
    const secretPatterns = [
      /password\s*=\s*['"`][^'"`]+['"`]/gi,
      /api_key\s*=\s*['"`][^'"`]+['"`]/gi,
      /secret\s*=\s*['"`][^'"`]+['"`]/gi,
      /token\s*=\s*['"`][^'"`]+['"`]/gi,
    ];
    
    const files = await this.getAllCodeFiles(codePath);
    
    for (const file of files) {
      const content = await fs.readFile(file, 'utf8');
      
      for (const pattern of secretPatterns) {
        const matches = content.match(pattern);
        if (matches) {
          secrets.push({
            type: 'HARDCODED_SECRET',
            severity: 'HIGH',
            file: file,
            line: this.getLineNumber(content, matches[0]),
            code: matches[0],
            recommendation: 'Use environment variables or secure storage',
          });
        }
      }
    }
    
    return secrets;
  }
}
```

---

## 📋 COMPLIANCE & REGULATIONS

### GDPR Compliance

#### Data Subject Rights
```typescript
// GDPR rights implementation
export class GDPRRights {
  async rightToAccess(userId: string): Promise<UserDataExport> {
    const userData = await this.getAllUserData(userId);
    
    return {
      personalData: userData.personal,
      learningData: userData.learning,
      interactionData: userData.interactions,
      metadata: {
        exportDate: new Date().toISOString(),
        recordCount: this.countRecords(userData),
      },
    };
  }
  
  async rightToRectification(userId: string, corrections: DataCorrection[]): Promise<void> {
    for (const correction of corrections) {
      await this.updateUserData(userId, correction.field, correction.newValue);
      await this.logDataCorrection(userId, correction);
    }
  }
  
  async rightToErasure(userId: string): Promise<void> {
    // Soft delete (retain for legal requirements)
    await this.anonymizeUserData(userId);
    
    // Hard delete after retention period
    await this.scheduleDataDeletion(userId, this.getRetentionPeriod());
    
    // Confirmation to user
    await this.confirmDataErasure(userId);
  }
  
  async rightToPortability(userId: string): Promise<DataExport> {
    const userData = await this.rightToAccess(userId);
    
    return {
      format: 'JSON',
      data: userData,
      schema: 'teachit-data-schema-v1.0',
    };
  }
  
  async rightToObjection(userId: string, processingType: string): Promise<void> {
    await this.stopDataProcessing(userId, processingType);
    await this.logObjection(userId, processingType);
  }
}
```

### Educational Data Privacy

#### FERPA Compliance (US)
```typescript
// FERPA compliance implementation
export class FERPACompliance {
  async ensurePrivacy(studentId: string): Promise<PrivacyStatus> {
    const status: PrivacyStatus = {
      studentId,
      timestamp: new Date().toISOString(),
      checks: [],
      compliant: true,
    };
    
    // Check directory information
    const directoryCheck = await this.checkDirectoryInformation(studentId);
    status.checks.push(directoryCheck);
    
    // Check educational records
    const recordsCheck = await this.checkEducationalRecords(studentId);
    status.checks.push(recordsCheck);
    
    // Check parental access
    const parentalCheck = await this.checkParentalAccess(studentId);
    status.checks.push(parentalCheck);
    
    status.compliant = status.checks.every(check => check.compliant);
    
    return status;
  }
  
  private async checkEducationalRecords(studentId: string): Promise<ComplianceCheck> {
    const records = await this.getEducationalRecords(studentId);
    
    return {
      type: 'EDUCATIONAL_RECORDS',
      compliant: this.validateEducationalRecords(records),
      details: {
        recordCount: records.length,
        accessLevel: this.getAccessLevel(records),
        lastAccessed: this.getLastAccessed(records),
      },
    };
  }
}
```

---

## 🔧 SECURITY BEST PRACTICES

### Development Security

#### Secure Coding Guidelines
```typescript
// Security coding standards
export const securityGuidelines = {
  authentication: [
    'Use strong password policies',
    'Implement multi-factor authentication',
    'Use secure session management',
    'Implement proper logout functionality',
  ],
  
  dataProtection: [
    'Encrypt sensitive data at rest',
    'Use HTTPS for all communications',
    'Implement proper input validation',
    'Use parameterized queries',
  ],
  
  errorHandling: [
    'Don\'t expose sensitive information in error messages',
    'Log security events appropriately',
    'Implement graceful error handling',
    'Use generic error messages for users',
  ],
  
  configuration: [
    'Use environment variables for secrets',
    'Implement proper CORS policies',
    'Use secure headers',
    'Disable unnecessary features',
  ],
};
```

#### Security Testing Checklist
```typescript
// Security testing checklist
export const securityChecklist = {
  authentication: [
    'Password strength requirements',
    'Account lockout mechanisms',
    'Session timeout implementation',
    'Multi-factor authentication',
    'Secure password reset',
  ],
  
  authorization: [
    'Role-based access control',
    'Least privilege principle',
    'Resource access validation',
    'API endpoint protection',
    'Cross-origin resource sharing',
  ],
  
  dataProtection: [
    'Data encryption at rest',
    'Data encryption in transit',
    'Secure key management',
    'Data retention policies',
    'Privacy by design',
  ],
  
  infrastructure: [
    'Network security configuration',
    'Server hardening',
    'Database security',
    'Backup encryption',
    'Monitoring and logging',
  ],
};
```

---

## 📊 SECURITY METRICS

### Key Performance Indicators

#### Security Metrics
```typescript
// Security KPIs
export const securityMetrics = {
  authentication: {
    'Failed login attempts': 'count per hour',
    'Account lockouts': 'count per day',
    'MFA adoption rate': 'percentage',
    'Password reset requests': 'count per day',
  },
  
  authorization: {
    'Access denied events': 'count per hour',
    'Permission changes': 'count per day',
    'Role assignments': 'count per week',
    'Privilege escalation attempts': 'count per day',
  },
  
  dataProtection: {
    'Data encryption coverage': 'percentage',
    'Data access violations': 'count per day',
    'PII exposure incidents': 'count per month',
    'Data retention compliance': 'percentage',
  },
  
  incidents: {
    'Security incidents': 'count per month',
    'Incident response time': 'minutes',
    'Vulnerability remediation time': 'days',
    'Security testing coverage': 'percentage',
  },
};
```

#### Security Dashboard
```typescript
// Security monitoring dashboard
export class SecurityDashboard {
  async getSecurityMetrics(): Promise<SecurityMetrics> {
    return {
      authentication: await this.getAuthenticationMetrics(),
      authorization: await this.getAuthorizationMetrics(),
      dataProtection: await this.getDataProtectionMetrics(),
      incidents: await this.getIncidentMetrics(),
      compliance: await this.getComplianceMetrics(),
    };
  }
  
  private async getAuthenticationMetrics(): Promise<AuthMetrics> {
    const now = new Date();
    const hourAgo = new Date(now.getTime() - 60 * 60 * 1000);
    
    const failedLogins = await this.countFailedLogins(hourAgo, now);
    const accountLockouts = await this.countAccountLockouts(hourAgo, now);
    const mfaAdoption = await this.calculateMFAAdoption();
    
    return {
      failedLogins,
      accountLockouts,
      mfaAdoption,
      passwordResets: await this.countPasswordResets(hourAgo, now),
    };
  }
}
```

---

## 📞 SECURITY CONTACTS

### Security Team

#### Incident Response Team
- **Security Lead**: security@teachit.app
- **Incident Response**: incidents@teachit.app
- **Vulnerability Reports**: vulnerabilities@teachit.app
- **Compliance Officer**: compliance@teachit.app

#### Emergency Contacts
- **Critical Incidents**: +1-800-SECURITY
- **Data Breach**: +1-800-BREACH
- **Legal Counsel**: legal@teachit.app
- **Law Enforcement**: emergency@teachit.app

### Reporting Security Issues

#### Vulnerability Disclosure
- **Email**: security@teachit.app
- **PGP Key**: Available on request
- **Response Time**: Within 24 hours
- **Bounty Program**: Available for qualifying reports

#### Data Subject Requests
- **Access Requests**: privacy@teachit.app
- **Deletion Requests**: delete@teachit.app
- **Correction Requests**: corrections@teachit.app
- **Complaints**: complaints@teachit.app

---

## ✅ SECURITY CHECKLIST

### Daily Security Checks
- [ ] Review security logs for anomalies
- [ ] Monitor failed authentication attempts
- [ ] Check system resource utilization
- [ ] Verify backup completion
- [ ] Review access request approvals

### Weekly Security Reviews
- [ ] Analyze security metrics trends
- [ ] Review incident reports
- [ ] Update threat intelligence
- [ ] Check compliance status
- [ ] Review security patch status

### Monthly Security Audits
- [ ] Conduct vulnerability scans
- [ ] Review access controls
- [ ] Update security policies
- [ ] Perform penetration testing
- [ ] Review data retention compliance

### Quarterly Security Assessments
- [ ] Full security audit
- [ ] Risk assessment update
- [ ] Security training review
- [ ] Compliance audit
- [ ] Incident response drill

---

*Last Updated: 2026-05-06*
*Version: 1.0.0*
*Security Team: Information Security*