Post-Migration Security

After completing migration, security hardening ensures the improved system remains protected. Remove all legacy hashing code to prevent accidental reuse. Archive legacy password data securely in case of unforeseen issues, but ensure it's not accessible to production systems. Implement alerts for any attempts to use legacy authentication methods.

Force password resets for accounts that never authenticated during the migration period. These dormant accounts pose security risks as their passwords remain hashed with legacy algorithms. Implement risk-based reset requirements—high-privilege accounts might require immediate reset, while low-risk accounts could have extended grace periods.

class PostMigrationSecurity:
    """Security hardening after migration completion"""
    
    def __init__(self, auth_system, migration_log):
        self.auth_system = auth_system
        self.migration_log = migration_log
        
    def execute_post_migration_hardening(self):
        """Execute comprehensive post-migration security steps"""
        
        results = {
            'start_time': datetime.now(),
            'actions_taken': []
        }
        
        # 1. Identify never-migrated accounts
        dormant_accounts = self._identify_dormant_accounts()
        results['dormant_accounts'] = len(dormant_accounts)
        
        # 2. Force reset for high-risk dormant accounts
        for account in dormant_accounts:
            if self._is_high_risk_account(account):
                self.auth_system.force_password_reset(account['username'])
                results['actions_taken'].append(f"Forced reset: {account['username']}")
        
        # 3. Disable legacy endpoints
        self._disable_legacy_endpoints()
        results['actions_taken'].append("Disabled legacy authentication endpoints")
        
        # 4. Archive legacy data
        archive_location = self._archive_legacy_data()
        results['archive_location'] = archive_location
        
        # 5. Update security policies
        self._update_security_policies()
        
        # 6. Implement monitoring
        self._setup_legacy_attempt_monitoring()
        
        results['end_time'] = datetime.now()
        results['success'] = True
        
        return results
    
    def _identify_dormant_accounts(self) -> List[Dict]:
        """Find accounts that never migrated"""
        
        all_users = self.auth_system.get_all_users()
        migrated_users = set(self.migration_log.get_migrated_usernames())
        
        dormant = []
        for user in all_users:
            if user['username'] not in migrated_users:
                dormant.append({
                    'username': user['username'],
                    'last_login': user.get('last_login'),
                    'created_date': user.get('created_date'),
                    'privilege_level': user.get('role', 'user')
                })
        
        return dormant
    
    def _is_high_risk_account(self, account: Dict) -> bool:
        """Determine if account is high-risk"""
        
        # Admin or privileged accounts
        if account['privilege_level'] in ['admin', 'administrator', 'root']:
            return True
        
        # Service accounts
        if 'service' in account['username'] or 'api' in account['username']:
            return True
        
        # Old accounts (created > 2 years ago, never logged in recently)
        if account['created_date']:
            age = (datetime.now() - account['created_date']).days
            if age > 730 and not account['last_login']:
                return True
        
        return False
    
    def _setup_legacy_attempt_monitoring(self):
        """Monitor for attempts to use legacy authentication"""
        
        # Create alert rules
        alert_rules = [
            {
                'name': 'legacy_hash_attempt',
                'condition': 'password_hash_algorithm == "md5" OR password_hash_algorithm == "sha1"',
                'action': 'alert_security_team',
                'severity': 'high'
            },
            {
                'name': 'legacy_endpoint_access',
                'condition': 'endpoint LIKE "/api/v1/auth%" OR endpoint LIKE "/legacy/%"',
                'action': 'block_and_alert',
                'severity': 'critical'
            }
        ]
        
        for rule in alert_rules:
            self.auth_system.add_monitoring_rule(rule)

Migrating legacy password systems requires balancing security improvements with operational reality. While the technical challenges are significant—handling character encodings, managing large databases, and maintaining service availability—the human factors often prove more complex. Success requires careful planning, phased execution, and clear communication with affected users. By following structured migration approaches and learning from common pitfalls, organizations can modernize their authentication infrastructure without disrupting business operations. The investment in proper migration pays dividends through improved security, reduced support burden, and compliance with modern standards.## Performance Optimization and Scaling Considerations

Password hashing deliberately introduces computational overhead to frustrate attackers, but this same property creates performance challenges at scale. Organizations processing thousands of authentication requests per second must balance security requirements with system responsiveness. This chapter explores techniques for optimizing password hashing performance without compromising security, covering hardware acceleration, caching strategies, distributed architectures, and capacity planning for growing systems.