Detect Multi-Factor Authentication in Google Chronicle
Adversaries may disable or modify multi-factor authentication (MFA) mechanisms to enable persistent access to compromised accounts. Methods include: excluding users from Azure AD Conditional Access Policies, registering adversary-controlled MFA methods (Scattered Spider), modifying Windows hosts file to redirect MFA server calls to localhost causing fail-open behavior (CISA AA22-074A), using AADInternals Set-AADIntUserMFA to disable MFA, and modifying SLOWPULSE to bypass RADIUS/ACE 2FA. Detection focuses on MFA configuration changes in identity provider audit logs.
MITRE ATT&CK
- Technique
- T1556 Modify Authentication Process
- Sub-technique
- T1556.006 Multi-Factor Authentication
- Canonical reference
- https://attack.mitre.org/techniques/T1556/006/
YARA-L Detection Query
rule mfa_modification_t1556_006 {
meta:
author = "Detection Engineering"
description = "Detects MFA disable/modification and Conditional Access policy changes in Azure AD audit logs mapped to Chronicle UDM"
mitre_attack_technique = "T1556.006"
mitre_attack_tactic = "Persistence, Defense Evasion, Credential Access"
severity = "HIGH"
reference = "https://attack.mitre.org/techniques/T1556/006/"
events:
$e.metadata.vendor_name = "Microsoft"
$e.metadata.product_event_type =~ "(?i)(Disable StrongAuthentication|User registered security info|User deleted security info|Admin deleted security info|Admin disabled MFA|Update per-user MFA|Add conditional access policy|Update conditional access policy|Delete conditional access policy)"
$e.principal.user.userid = $actor
condition:
$e
}Chronicle YARA-L 2.0 rule detecting T1556.006 MFA modification events in UDM-mapped Azure AD audit logs. Fires on StrongAuthentication disable operations, admin-initiated security info deletion, per-user MFA updates, and Conditional Access policy lifecycle events. Requires the Microsoft Azure AD audit log parser to be enabled in the Chronicle ingestion pipeline.
Data Sources
Required Tables
False Positives & Tuning
- Authorised identity administrators performing bulk MFA policy migrations from legacy per-user MFA enforcement to Conditional Access-based MFA, generating multiple policy change events in quick succession
- Security team testing Conditional Access policy logic in a non-production tenant whose audit events replicate into the same Chronicle instance used for production detections
- Break-glass emergency account procedures that temporarily add privileged accounts to Conditional Access exclusion groups during critical outage response, creating policy update events outside normal business hours
Other platforms for T1556.006
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 MFA for a User via Microsoft Graph API
Expected signal: Azure AD Audit Log: OperationName 'User deleted security info' or 'Update user' with StrongAuthenticationRequirement modification. Graph API call logged in Azure AD diagnostic logs. PowerShell ScriptBlock Log Event ID 4104.
- Test 2Add Trusted Location to Conditional Access Policy
Expected signal: Azure AD Audit Log: OperationName 'Add named location' with the new IP range visible in audit details. Azure AD Audit Log: If location is then added as exclusion to a CA policy, OperationName 'Update conditional access policy'.
- Test 3Modify Windows Hosts File to Redirect MFA Server (CISA AA22-074A Pattern)
Expected signal: Sysmon Event ID 11 (File Create/Modify): TargetFilename=C:\Windows\System32\drivers\etc\hosts, initiated by powershell.exe. Windows Defender may alert on hosts file modification. Security Event ID 4663 if file auditing is enabled.
References (6)
- https://attack.mitre.org/techniques/T1556/006/
- https://www.cisa.gov/uscert/ncas/alerts/aa22-074a
- https://www.mandiant.com/media/17826
- https://docs.microsoft.com/en-us/azure/active-directory/governance/conditional-access-exclusion
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1556.006/T1556.006.md
- https://www.microsoft.com/en-us/security/blog/2022/10/25/microsoft-incident-response-tips-for-managing-a-phishing-crisis/
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