Restrict Guest Access to Allowlisted Domains for Government & Public Sector
How government & public sector organizations should implement EXT-03 for Microsoft 365 security and compliance.
For government & public sector companies using Microsoft 365, restrict guest access to allowlisted domains is a security priority. This guide explains how EXT-03 helps government & public sector organizations protect their identity infrastructure while meeting industry-specific compliance mandates.
Why Government & Public Sector Organizations Need This Control
Government & Public Sector organizations face specific regulatory requirements including fedramp, nist-800-53, cis. The EXT-03 control helps address these requirements by:
- Guest invitations are restricted to an allowlist of trusted domains
- Cross-tenant access policies block all other external tenants
- External sharing in SharePoint/OneDrive is restricted to allowed domains
At Level 3, external collaboration is tightly controlled. Only pre-approved partner organizations can access your tenant. This prevents social engineering and limits data exposure to vetted third parties.
Industry-Specific Considerations
When implementing EXT-03 in a government & public sector environment, consider:
- **Regulatory requirements**: fedramp, nist-800-53, cis may mandate specific configurations
- **Risk tolerance**: Government & Public Sector organizations typically have moderate to low risk tolerance
- **Audit frequency**: Plan for regular compliance reviews
- **Documentation**: Maintain detailed records for regulatory inspections
How to Configure
EXT-03 requires the following configuration:
- Guest invitations are restricted to an allowlist of trusted domains
- Cross-tenant access policies block all other external tenants
- External sharing in SharePoint/OneDrive is restricted to allowed domains
Remediation is manual: no domain-allowlist action exists, so there is no safe auto-fix yet. TrueConfig provides a step-by-step script/guide to configure the guest domain allowlist and cross-tenant access policies.
Follow the steps above in your Microsoft Entra admin center to enable this control.
Government Compliance Requirements
Government organizations must comply with these frameworks, all of which address restrict guest access to allowlisted domains:
Why This Control Matters for Government
At Level 3, external collaboration is tightly controlled. Only pre-approved partner organizations can access your tenant. This prevents social engineering and limits data exposure to vetted third parties.
Common threats in government & public sector:
- • Nation-state espionage campaigns
- • Ransomware targeting critical services
- • Insider threats from privileged users
For government & public sector organizations, EXT-03 is a key component of a compliant Microsoft 365 security posture. TrueConfig helps you implement and maintain this control while meeting industry-specific requirements.
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