cis-azure-foundations-5.2.5

Ensure multifactor authentication is required for risky sign-ins

Description

Entra ID tracks the behavior of sign-in events. If the Entra ID domain is licensed with P2, the sign-in behavior can be used as a detection mechanism for additional scrutiny during the sign-in event. If this policy is set up, then Risky Sign-in events will prompt users to use multi-factor authentication (MFA) tokens on login for additional verification.

Rationale

Enabling multi-factor authentication is a recommended setting to limit the potential of accounts being compromised and limiting access to authenticated personnel. Enabling this policy allows Entra ID's risk-detection mechanisms to force additional scrutiny on the login event, providing a deterrent response to potentially malicious sign-in events, and adding an additional authentication layer as a reaction to potentially malicious behavior.

Impact

Risk Policies for Conditional Access require Microsoft Entra ID P2. Additional overhead to support or maintain these policies may also be required if users lose access to their MFA tokens.

Audit Procedure

Using Azure Portal

1. From Azure Home select the Portal Menu in the top left and select Microsoft Entra ID.
2. Select Security.
3. Select on the left side Conditional Access.
4. Select Policies.
5. Select the policy you wish to audit.
6. Click the blue text under Users.
7. View under Include the corresponding users and groups to whom the policy is applied.
8. View under Exclude to determine which users and groups to whom the policy is not applied.

Expected Result

A Conditional Access policy should exist that requires MFA for risky sign-ins, targeting all users with all cloud apps, with sign-in risk conditions set to High and Medium, and the Grant control set to Require multifactor authentication with sign-in frequency set to Every time.

Remediation

Remediate from Azure Portal

1. From Azure Home select the Portal Menu in the top left and select Microsoft Entra ID.
2. Select Security.
3. Select Conditional Access.
4. Select Policies.
5. Click + New policy.
6. Enter a name for the policy.
7. Click the blue text under Users.
8. Under Include, select All users.
9. Under Exclude, check Users and groups.
10. Select users this policy should not apply to and click Select.
11. Click the blue text under Target resources.
12. Select All cloud apps.
13. Click the blue text under Conditions.
14. Select Sign-in risk.
15. Update the Configure toggle to Yes.
16. Check the sign-in risk level this policy should apply to, e.g. High and Medium.
17. Select Done.
18. Click the blue text under Grant and check Require multifactor authentication then click the Select button.
19. Click the blue text under Session then check Sign-in frequency and select Every time and click the Select button.
20. Set Enable policy to Report-only.
21. Click Create.

After testing the policy in report-only mode, update the Enable policy setting from Report-only to On.

Default Value

MFA is not enabled by default.

References

1. https://learn.microsoft.com/en-us/entra/identity/conditional-access/policy-risk-based-sign-in
2. https://learn.microsoft.com/en-us/entra/identity/conditional-access/troubleshoot-conditional-access-what-if
3. https://learn.microsoft.com/en-us/entra/identity/conditional-access/howto-conditional-access-insights-reporting
4. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-identity-management#im-7-restrict-resource-access-based-on--conditions
5. https://learn.microsoft.com/en-us/entra/id-protection/overview-identity-protection#license-requirements

CIS Controls

Profile

Level 2 | Manual