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Google Workspace Organizational Unit Security Design¶

This guide provides security professionals and MSPs with comprehensive strategies for designing and implementing secure organizational unit (OU) structures in Google Workspace environments. Proper OU design is fundamental to effective security implementation and management.

Organizational Unit Fundamentals¶

Understanding OU Architecture¶

Organizational Units in Google Workspace provide a hierarchical structure for managing users, applying policies, and controlling access. Key concepts include:

Inheritance Model
Settings flow from parent OUs to child OUs
Child OUs inherit settings unless explicitly overridden
Inheritance can be selectively blocked for specific settings
Default Configuration
All Google Workspace accounts start with a root OU
All users initially belong to the root OU
Settings applied at the root level affect all users by default
Access Control Implications
OU structure determines policy application
Admin privileges can be scoped to specific OUs
Service availability controlled at the OU level

OU Security Design Principles¶

When designing a secure OU structure, follow these core principles:

Least Privilege Model
Group users based on required access levels
Apply restrictions at the highest possible level
Grant exceptions only where necessary
Administrative Segregation
Separate administrative boundaries
Delegate admin rights at appropriate OU levels
Implement administrative isolation for sensitive departments
Security Consistency
Maintain consistent security controls across similar OUs
Document security baselines for each OU level
Implement change control for OU structure modifications
Operational Efficiency
Balance security with management overhead
Design for scalability as organization grows
Minimize exceptions and special cases

Strategic OU Design Patterns¶

Pattern 1: Security-Oriented Hierarchy¶

This pattern prioritizes security boundaries and regulatory compliance:

Root
├── Security Tier 1 (Highest Security)
│   ├── Executive Leadership
│   ├── Finance
│   └── Legal
├── Security Tier 2 (Enhanced Security)
│   ├── Engineering
│   ├── Product Management
│   └── Human Resources
├── Security Tier 3 (Standard Security)
│   ├── Marketing
│   ├── Sales
│   └── Customer Support
└── Special Access
    ├── Contractors
    ├── Partners
    └── Temporary

Implementation Considerations: - Apply MFA requirements consistently within each tier - Implement stricter data controls as you move up the hierarchy - Configure service access based on security requirements

Pattern 2: Functional Hierarchy¶

This pattern organizes OUs based on department function:

Root
├── Corporate Services
│   ├── Executive
│   ├── Finance
│   ├── HR
│   └── Legal
├── Revenue Generation
│   ├── Sales
│   ├── Marketing
│   └── Business Development
├── Product Development
│   ├── Engineering
│   ├── Product Management
│   └── Design
├── Customer Operations
│   ├── Support
│   ├── Success
│   └── Training
└── External Collaborators
    ├── Vendors
    ├── Partners
    └── Contractors

Implementation Considerations: - Apply security policies based on department-specific risks - Customize service access by functional requirements - Implement data sharing controls between departments

Pattern 3: Geographic Hierarchy¶

For organizations with regional security or compliance requirements:

Root
├── North America
│   ├── USA (CCPA Compliant)
│   │   ├── HQ
│   │   └── Remote
│   └── Canada (PIPEDA Compliant)
├── Europe (GDPR Compliant)
│   ├── EU Members
│   └── UK
├── Asia Pacific
│   ├── Australia
│   ├── Singapore
│   └── Japan
└── Global Roles
    ├── Executive
    ├── IT Administration
    └── Security

Implementation Considerations: - Apply region-specific compliance settings at regional OUs - Implement appropriate data residency controls - Configure service access based on regional availability

Pattern 4: Multi-Tenant MSP Structure¶

For MSPs managing multiple client environments:

Root
├── MSP Internal
│   ├── Administration
│   ├── Engineering
│   ├── Support
│   └── Management
├── Client Tier 1 (Enterprise)
│   ├── Client A
│   │   ├── Admin
│   │   ├── Standard
│   │   └── Restricted
│   └── Client B
│       ├── Admin
│       ├── Standard
│       └── Restricted
├── Client Tier 2 (Mid-Market)
│   ├── Client C
│   └── Client D
└── Client Tier 3 (Small Business)
    ├── Client E
    └── Client F

Implementation Considerations: - Implement strong isolation between client environments - Apply standardized security baselines by client tier - Configure delegated administration with appropriate boundaries

Security Controls by OU Layer¶

For each layer in your OU hierarchy, implement appropriate security controls:

Root-Level Controls (All Users)¶

Security Control	Implementation	Rationale
Password Policy	Minimum 12 characters, complexity requirements	Baseline security for all accounts
Basic MFA	Require 2-Step Verification	Fundamental protection against account compromise
Session Management	Configure appropriate timeout settings	Basic security hygiene
Account Recovery	Standardize recovery options	Consistent recovery procedures
Acceptable Use	Apply organization-wide policies	Baseline compliance

Enhanced Security OU Controls¶

Security Control	Implementation	Rationale
Advanced MFA	Require security keys	Stronger protection for sensitive roles
Access Context	Implement context-aware access policies	Adaptive security based on risk
Device Management	Require managed devices	Control endpoint security
Data Controls	Implement stricter DLP policies	Protect sensitive information
External Sharing	Restrict sharing capabilities	Prevent data leakage

High-Security OU Controls¶

Security Control	Implementation	Rationale
Security Keys Only	Enforce FIDO security keys	Maximum authentication security
Advanced Protection	Enroll in Advanced Protection Program	Comprehensive protection for critical accounts
IP Restriction	Limit access to specific networks	Network-level access control
Enhanced Auditing	Implement comprehensive logging	Detailed visibility for sensitive activities
External Access	Severely restrict external sharing	Strict data boundary enforcement

Contractor/External OU Controls¶

Security Control	Implementation	Rationale
Service Limitation	Restrict access to necessary services only	Minimize attack surface
Data Access Controls	Implement granular access controls	Strict need-to-know access
Extended Verification	Additional authentication challenges	Higher-risk accounts
Time-Based Access	Implement limited access windows	Temporal privilege restriction
Auto-Expiration	Configure account expiration	Automated deprovisioning

Best Practices for OU Security Implementation¶

1. OU Migration Planning¶

When implementing or restructuring OUs:

Assessment Phase
Document current state including users, groups, and policies
Identify security gaps in existing structure
Define security objectives for new structure
Design Phase
Create comprehensive OU diagram with security boundaries
Define inheritance model and override points
Document policy application by OU level
Testing Phase
Validate policy inheritance in test environment
Verify administrative boundaries function as expected
Test user experience for each OU level
Implementation Phase
Develop staged migration plan
Create communication plan for affected users
Implement controlled rollout with validation

2. OU Security Governance¶

Establish governance processes for OU management:

Documentation Requirements
Maintain up-to-date OU structure documentation
Document security baselines for each OU level
Maintain policy exception register
Change Control
Implement formal change process for OU structure modifications
Require security review for policy changes
Maintain audit trail of structural changes
Regular Review Cycle
Conduct quarterly OU structure reviews
Validate security control effectiveness
Assess user placement appropriateness
Compliance Mapping
Document how OU structure supports compliance requirements
Map controls to regulatory frameworks
Validate compliance control effectiveness

3. OU Administrative Model¶

Implement a secure administrative model for OU management:

Role-Based Administration
Define administrative roles aligned with OU structure
Implement least privilege for admin accounts
Create separation of duties between admin functions
Delegated Administration
Delegate specific admin functions to appropriate teams
Scope admin access to specific OUs
Implement strict controls for root-level administration
Administrative Monitoring
Log all administrative actions at OU level
Implement alerting for critical OU changes
Conduct regular admin access reviews
Emergency Access Procedures
Define break-glass procedures for emergency access
Create secure process for emergency OU changes
Implement post-incident review requirements

Advanced OU Security Techniques¶

Dynamic OU Assignment¶

Implement rule-based user assignment to OUs:

Attribute-Based Assignment
Develop automation to assign users based on HR attributes
Create rules for department, role, or location-based assignment
Implement review process for assignment exceptions
Risk-Based OU Movement
Develop criteria for moving users between security tiers
Implement automated risk scoring
Create process for handling high-risk user indicators
Temporary Elevation
Design process for temporary OU reassignment
Implement time-bound access to higher-privilege OUs
Create audit mechanisms for tracking temporary changes

Security Inheritance Controls¶

Implement advanced inheritance management:

Inheritance Documentation
Map all inheritance overrides across OU structure
Document business justification for inheritance blocks
Maintain visualization of inheritance relationships
Inheritance Monitoring
Create alerts for critical inheritance changes
Implement regular validation of inheritance configuration
Develop reports highlighting inheritance exceptions
Compliance Inheritance
Implement specialized inheritance rules for compliance requirements
Create compliance-specific OUs where necessary
Document inheritance implications for auditors

MSP-Specific OU Strategies¶

Multi-Tenant OU Management¶

For MSPs managing multiple client environments:

Client Isolation
Implement strict boundaries between client OUs
Create separate administrative accounts per client
Configure distinct security baselines by client
Standardized Substructures
Develop templated OU structures for new clients
Create standard security tiers applicable across clients
Implement consistent naming conventions
Cross-Client Visibility
Design appropriate MSP admin visibility across clients
Implement security monitoring across OU boundaries
Create aggregated reporting capabilities

Client Onboarding Procedures¶

Establish secure client implementation processes:

OU Structure Design
Conduct client security requirements workshop
Design appropriate OU structure based on needs
Document client-specific security requirements
Security Baseline Implementation
Apply appropriate tier-based security controls
Configure custom policies as required
Implement client-specific exceptions with documentation
Administrative Delegation
Configure appropriate client admin access
Establish MSP admin boundaries
Document administrative responsibilities

Common OU Security Misconfigurations¶

Anti-Pattern 1: Flat OU Structure¶

Issue: Using minimal OUs with extensive exceptions Risk: Inconsistent policy application, excessive administrative overhead Remediation: - Implement hierarchical structure based on security requirements - Group users with similar security needs - Apply exceptions at appropriate OU levels rather than individually

Anti-Pattern 2: Excessive OU Depth¶

Issue: Creating unnecessary levels of OU nesting Risk: Complex management, inheritance problems, troubleshooting difficulties Remediation: - Limit OU depth to 3-4 levels when possible - Focus on functional rather than organizational depth - Document inheritance clearly for deep structures

Anti-Pattern 3: Inconsistent Inheritance¶

Issue: Unpredictable blocking of inherited settings Risk: Security gaps, unintended policy application Remediation: - Document all inheritance overrides - Implement review process for inheritance changes - Regularly audit effective settings at leaf OUs

Anti-Pattern 4: Administrative Boundary Failures¶

Issue: Improper scoping of administrative access Risk: Privilege escalation, unauthorized access to sensitive OUs Remediation: - Implement strict administrative boundaries - Regularly review admin access scope - Audit administrative actions across boundaries

Implementation Checklist¶

Initial OU Security Setup¶

Document business requirements for OU structure
Design OU hierarchy based on security needs
Define security policies for each OU level
Create OU structure in test environment
Validate policy inheritance works as expected
Implement administrative boundaries
Document and review with stakeholders
Migrate users to appropriate OUs

Regular Maintenance Tasks¶

Quarterly review of OU structure
Audit of user OU placements
Verification of policy inheritance
Review of administrative access
Validation of security control effectiveness
Update of OU documentation
Assessment of potential structure improvements

Security Monitoring for OUs¶

Critical Events to Monitor¶

Event Type	Description	Risk Indication
OU Creation/Deletion	New OUs being created or removed	Potential structure manipulation
OU Moving	OUs being relocated in hierarchy	Inheritance changes, potential policy bypass
User Moving	Users moving between OUs	Security policy changes, potential privilege change
Inheritance Override	Changes to policy inheritance	Potential security control bypass
Admin Privilege Changes	Changes to admin access for OUs	Potential privilege escalation

Sample Monitoring Queries¶

Detecting Unusual OU Changes:

SELECT admin_email, event_type, target_ou_name, timestamp
FROM admin_audit_logs
WHERE event_type IN ('CREATE_OU', 'DELETE_OU', 'MOVE_OU')
  AND timestamp > TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 7 DAY)
  AND admin_email NOT IN (SELECT admin_email FROM authorized_ou_admins)
ORDER BY timestamp DESC

Monitoring High-Risk User Movement:

SELECT admin_email, affected_user_email, 
       source_ou_path, destination_ou_path, timestamp
FROM admin_audit_logs
WHERE event_type = 'MOVE_USER'
  AND (
    -- Moving from restricted to less restricted
    (source_ou_path LIKE '%/HighSecurity/%' AND destination_ou_path NOT LIKE '%/HighSecurity/%')
    OR
    -- Moving to administrative OUs
    (destination_ou_path LIKE '%/Admin/%')
  )
  AND timestamp > TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 7 DAY)
ORDER BY timestamp DESC

Tracking Inheritance Changes:

SELECT admin_email, target_ou_path, setting_name, 
       old_value, new_value, timestamp
FROM admin_audit_logs
WHERE event_type = 'CHANGE_SETTING_INHERITANCE'
  AND setting_name IN ('Password Strength', 'Two Factor Authentication', 'Access Controls', 'Data Controls')
  AND timestamp > TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 7 DAY)
ORDER BY timestamp DESC

Resources¶

Note: This guide should be adapted to your organization's specific needs, size, and security requirements.