Detect Conditional Access Policies in Google Chronicle
Adversaries may disable or modify Conditional Access Policies (CAP) to enable persistent access to compromised accounts. Conditional Access applies additional verification based on IP, device enrollment, MFA, and risk-based signals. Attackers modify CAPs by adding trusted IP ranges (Scattered Spider added attacker-controlled IPs), removing MFA requirements, adding user exclusions, or disabling policies. Storm-0501 circumvented CAPs using hybrid-joined servers. In AWS/GCP, IAM condition attributes can be weakened by removing IP or time-of-day restrictions.
MITRE ATT&CK
- Technique
- T1556 Modify Authentication Process
- Sub-technique
- T1556.009 Conditional Access Policies
- Canonical reference
- https://attack.mitre.org/techniques/T1556/009/
YARA-L Detection Query
rule t1556_009_conditional_access_policy_modification {
meta:
author = "Detection Engineering"
description = "Detects Azure AD Conditional Access Policy and Named Location lifecycle events indicative of T1556.009 — persistence via CAP weakening"
mitre_attack_tactic = "Persistence"
mitre_attack_technique = "T1556.009"
severity = "HIGH"
confidence = "HIGH"
rule_version = "1.0"
events:
$e.metadata.log_type = "AZURE_AD_AUDIT"
$e.metadata.product_event_type in (
"Add conditional access policy",
"Update conditional access policy",
"Delete conditional access policy",
"Add named location",
"Update named location",
"Delete named location"
)
$actor = $e.principal.user.userid
$policy = $e.target.resource.name
$op = $e.metadata.product_event_type
condition:
$e
}Chronicle YARA-L 2.0 rule detecting Azure AD Conditional Access Policy and Named Location modifications via the AZURE_AD_AUDIT log type. Matches the six key operation types used by adversaries to weaken CAP enforcement. Extracts actor UPN, target resource name, and operation type as rule variables for use in alerting and enrichment. Covers Scattered Spider and Storm-0501 TTPs.
Data Sources
Required Tables
False Positives & Tuning
- Azure AD Global Administrators or Security Administrators conducting quarterly policy reviews and updating IP allowlists
- Microsoft Entra ID Governance workflows that automatically update CAP exclusion groups during access review completions
- Infrastructure-as-code deployments via Azure DevOps pipelines using service principals with directory write permissions
Other platforms for T1556.009
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Disable a Non-Critical Conditional Access Policy
Expected signal: Azure AD Audit Log: OperationName 'Update conditional access policy', ModifiedProperties showing State changed from 'enabled' to 'disabled'. Actor logged as the authenticated Microsoft Graph session user.
- Test 2Add a Trusted Named Location (Simulating Scattered Spider TTP)
Expected signal: Azure AD Audit Log: OperationName 'Add named location', TargetResources showing the new location name and IP range. IsTrusted=true visible in audit details.
- Test 3Enumerate Existing Conditional Access Policies
Expected signal: Azure AD Audit Log: Read operation on conditional access policies. Microsoft Graph API call logged. PowerShell ScriptBlock Log Event ID 4104 with the Get-MgIdentityConditionalAccessPolicy command.
References (5)
- https://attack.mitre.org/techniques/T1556/009/
- https://learn.microsoft.com/en-us/entra/identity/conditional-access/overview
- https://docs.microsoft.com/en-us/azure/active-directory/governance/conditional-access-exclusion
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1556.009/T1556.009.md
- https://www.microsoft.com/en-us/security/blog/2023/10/25/octo-tempest-crosses-boundaries-to-facilitate-extortion-encryption-and-destruction/
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