[Rule Tuning] Microsoft Entra ID MFA TOTP Brute Force Attempts

rules/integrations/azure/credential_access_azure_entra_totp_brute_force_attempts.toml

@@ -2,90 +2,61 @@
 creation_date = "2024/12/11"
 integration = ["azure"]
 maturity = "production"
-updated_date = "2025/03/20"
+updated_date = "2025/07/28"
 
 [rule]
 author = ["Elastic"]
 description = """
 Identifies brute force attempts against Azure Entra multi-factor authentication (MFA) Time-based One-Time Password
 (TOTP) verification codes. This rule detects high frequency failed TOTP code attempts for a single user in a short
-time-span. Adversaries with valid credentials, when attempting to login to Azure portal or other Azure services, may be
-prompted to provide a TOTP code as part of the MFA process. If successful, adversaries can bypass MFA and gain
-unauthorized access to Azure resources.
+time-span with a high number of distinct session IDs. Adversaries may programmatically attemopt to brute-force TOTP
+codes by generating several sessions and attempt to guess the correct code.
 """
 false_positives = [
     """
     Based on the high-frequency threshold, it would be unlikely for a legitimate user to exceed the threshold for failed
-    TOTP code attempts in a short time-span.
+    TOTP code attempts in a short time-span over multiple sessions.
     """,
 ]
 from = "now-9m"
 language = "esql"
 license = "Elastic License v2"
-name = "Azure Entra MFA TOTP Brute Force Attempts"
+name = "Microsoft Entra ID MFA TOTP Brute Force Attempts"
 note = """## Triage and analysis
 
-### Investigating Azure Entra MFA TOTP Brute Force Attempts
+### Investigating Microsoft Entra ID MFA TOTP Brute Force Attempts
 
-This rule detects high-frequency failed TOTP code attempts for a single user in a short time span. Such behavior could indicate an adversary attempting to bypass multi-factor authentication (MFA) protections using valid credentials. Understanding the context of the user's typical behavior and identifying anomalies in the log data are critical to determining the nature of the activity.
+This rule detects brute force attempts against Azure Entra multi-factor authentication (MFA) Time-based One-Time Password (TOTP) verification codes. It identifies high-frequency failed TOTP code attempts for a single user in a short time-span with a high number of distinct session IDs. Adversaries may programmatically attempt to brute-force TOTP codes by generating several sessions and attempting to guess the correct code.
 
 #### Possible Investigation Steps:
 
-**Review the Source IP Address**:
-    - Check the `source.ip` or `azure.signinlogs.caller_ip_address` field.
-    - Determine if the IP address is associated with the user’s typical login locations.
+    - Check the source addresses associated with the failed TOTP attempts.
+    - Determine if the source IP address is consistent with the user’s typical login locations.
     - Look for unusual geographic patterns or anomalous IP addresses (e.g., proxies, VPNs, or locations outside the user’s normal activity).
-
-**Analyze User Activity**:
-    - Identify the user from the `azure.signinlogs.properties.sign_in_identifier` field.
-    - Determine if the user is currently active from another device or session. Session hijacking could explain parallel activity with failed attempts.
-    - Review past logs for the user to determine whether MFA failures or other anomalies are consistent or new.
-
-**Inspect the Authentication Method**:
-    - Evaluate the `azure.signinlogs.properties.mfa_detail.auth_method` field: `OATH verification code`.
-    - Confirm if the user typically uses TOTP codes or another MFA method (e.g., push notifications).
-    - Verify if there are any recent changes to the user’s MFA settings that may explain multiple failed attempts.
-
-**Evaluate the User Agent**:
-    - Check the `user_agent.original` field.
-    - Identify if the user agent matches a typical browser or a potentially malicious script (e.g., Python-based).
-    - Look for deviations in operating system or browser versions from the user’s normal activity.
-
-**Analyze Conditional Access Policies**:
-    - Review the `azure.signinlogs.properties.applied_conditional_access_policies` for enforced grant controls.
-    - Verify if MFA failures are tied to legitimate security policies (`display_name: Require multifactor authentication for admins`).
-
-**Correlate with Other Events**:
-    - Search for other authentication attempts involving the same `azure.signinlogs.caller_ip_address`, `user_principal_name`, or `azure.signinlogs.properties.app_id`.
-    - Look for suspicious activity patterns, such as password resets, privilege escalation, or account lockouts.
-
+    - Review the error code associated with the failed attempts. This can help identify if the failures are due to incorrect TOTP codes or other issues.
+    - Verify that that auth metho reported is `OAth` as it indicates the use of TOTP codes.
+    - Pivot into signin logs for the target user and check if auth via TOTP was successful which would indicate a successful brute force attempt.
+    - Review conditional access policies applied to the user or group as reported by the sign-in logs.
+    - Analyze the client application ID and display name to determine if the attempts are coming from a legitimate application or a potentially malicious script.
+        - Adversaries may use legitimate FOCI applications to bypass security controls or make login attempts appear legitimate.
+    - Review the resource ID access is being attempted against such as MyApps, Microsoft Graph, or other resources. This can help identify if the attempts are targeting specific applications or services.
+    - The correlation IDs or session IDs can be used to trace the authentication attempts across different logs or systems. Note that for this specific behavior, unique session ID count is high and could be challenging to correlate.
 
 #### False Positive Analysis:
 
-- **Unintentional User Behavior**:
     - Verify if the failed attempts could result from the user’s unfamiliarity with TOTP codes or issues with device synchronization.
     - Check if the user recently switched MFA methods or devices, which could explain multiple failures.
     - Determine if this is whitebox testing or a developer testing MFA integration.
 
-- **Administrative Actions**:
-    - Determine if the activity is related to legitimate administrative testing or configuration changes in the MFA system.
-
 #### Response and Remediation:
 
-- **Immediate Actions**:
     - If proven malicious, lock the affected account temporarily to prevent further unauthorized attempts.
     - Notify the user of suspicious activity and validate their access to the account.
     - Reset passwords and MFA settings for the affected user to prevent unauthorized access while communicating with the user.
-
-- **Strengthen Authentication Policies**:
     - Ensure conditional access policies are configured to monitor and restrict anomalous login behavior.
     - Consider a different MFA method or additional security controls to prevent future bypass attempts.
-
-- **Monitor and Audit**:
     - Implement additional monitoring to track high-frequency authentication failures across the environment.
     - Audit historical logs for similar patterns involving other accounts to identify broader threats.
-
-- **Educate and Train Users**:
     - Provide guidance on the secure use of MFA and the importance of recognizing and reporting suspicious activity.
 """
 references = [
@@ -95,16 +66,16 @@ references = [
 ]
 risk_score = 47
 rule_id = "3fac01b2-b811-11ef-b25b-f661ea17fbce"
-setup = """#### Required Azure Entra Sign-In Logs
-This rule requires the Azure logs integration be enabled and configured to collect all logs, including sign-in logs from Entra. In Entra, sign-in logs must be enabled and streaming to the Event Hub used for the Azure logs integration.
+setup = """#### Required Entra ID Sign-In Logs
+This rule requires the Entra ID sign-in logs via the Azure integration be enabled. In Entra ID, sign-in logs must be enabled and streaming to the Event Hub used for the Entra ID logs integration.
 """
 severity = "medium"
 tags = [
     "Domain: Cloud",
-    "Domain: SaaS",
+    "Domain: Identity",
     "Data Source: Azure",
     "Data Source: Entra ID",
-    "Data Source: Entra ID Sign-in",
+    "Data Source: Entra ID Sign-in logs",
     "Use Case: Identity and Access Audit",
     "Use Case: Threat Detection",
     "Tactic: Credential Access",
@@ -115,25 +86,76 @@ type = "esql"
 
 query = '''
 from logs-azure.signinlogs* metadata _id, _version, _index
+
 | where
     // filter for Entra Sign-In Logs
     event.dataset == "azure.signinlogs"
     and azure.signinlogs.operation_name == "Sign-in activity"
+    and azure.signinlogs.properties.user_type == "Member"
 
     // filter for MFA attempts with OATH conditional access attempts or TOTP
-    and azure.signinlogs.properties.authentication_requirement == "multiFactorAuthentication"
     and azure.signinlogs.properties.mfa_detail.auth_method == "OATH verification code"
 
     // filter on failures only from brute-force attempts
-    and azure.signinlogs.properties.conditional_access_status == "failure"
-    and azure.signinlogs.result_description == "Authentication failed during strong authentication request."
-| keep azure.signinlogs.properties.sign_in_identifier
+    and (
+            (
+                azure.signinlogs.result_signature == "FAILURE" and
+                azure.signinlogs.result_description == "Authentication failed during strong authentication request."
+            ) or azure.signinlogs.properties.status.error_code == 500121
+        )
+
 | stats
-    // aggregate by the sign-in account or principal
-    failed_totp_code_attempts = count(*) by azure.signinlogs.properties.sign_in_identifier
-| where
-    // filter on high frequency for a single user
-    failed_totp_code_attempts > 30
+    Esql.event_count = COUNT(*),
+    Esql.azure_signinlogs_properties.session_id_count_distinct = COUNT_DISTINCT(azure.signinlogs.properties.session_id),
+    Esql.source_address_values = VALUES(source.address),
+    Esql.azure_tenant_id_valuues = VALUES(azure.tenant_id),
+    Esql_priv.azure_identity_values = VALUES(azure.signinlogs.identity),
+    Esql_priv.azure_signinlogs_properties_user_principal_name_values = VALUES(azure.signinlogs.properties.user_principal_name),
+    Esql.azure_signinlogs_properties_app_id_values = VALUES(azure.signinlogs.properties.app_id),
+    Esql.azure_signinlogs_properties_app_display_name_values = VALUES(azure.signinlogs.properties.app_display_name),
+    Esql.azure_signinlogs_properties_authentication_requirement_values = VALUES(azure.signinlogs.properties.authentication_requirement),
+    Esql.azure_signinlogs_properties_authentication_protocol_values = VALUES(azure.signinlogs.properties.authentication_protocol),
+    Esql.azure_signinlogs_properties_client_app_used_values = VALUES(azure.signinlogs.properties.client_app_used),
+    Esql.azure_signinlogs_properties_client_credential_type_values = VALUES(azure.signinlogs.properties.client_credential_type),
+    Esql.azure_signinlogs_properties_conditional_access_status_values = VALUES(azure.signinlogs.properties.conditional_access_status),
+    Esql.azure_signinlogs_properties_correlation_id_values = VALUES(azure.signinlogs.properties.correlation_id),
+    Esql.azure_signinlogs_properties_is_interactive_values = VALUES(azure.signinlogs.properties.is_interactive),
+    Esql.azure_signinlogs_properties_mfa_detail_auth_method_values = VALUES(azure.signinlogs.properties.mfa_detail.auth_method),
+    Esql.azure_signinlogs_properties_resource_display_name_values = VALUES(azure.signinlogs.properties.resource_display_name),
+    Esql.azure_signinlogs_properties_resource_id_values = VALUES(azure.signinlogs.properties.resource_id),
+    Esql.azure_signinlogs_properties_risk_state_values = VALUES(azure.signinlogs.properties.risk_state),
+    Esql.azure_signinlogs_properties_risk_detail_values = VALUES(azure.signinlogs.properties.risk_detail),
+    Esql.azure_signinlogs_properties_status.error_code_values = VALUES(azure.signinlogs.properties.status.error_code),
+    Esql.azure_signinlogs_properties_original_request_id_values = VALUES(azure.signinlogs.properties.original_request_id),
+    Esql.user_id_values = VALUES(user.id)
+    by user.id
+
+| where Esql.event_count >= 20 and Esql.azure_signinlogs_properties.session_id_count_distinct >= 10
+
+| keep
+    Esql.event_count,
+    Esql.azure_signinlogs_properties.session_id_count_distinct,
+    Esql.source_address_values,
+    Esql.azure_tenant_id_valuues,
+    Esql_priv.azure_identity_values,
+    Esql_priv.azure_signinlogs_properties_user_principal_name_values,
+    Esql.azure_signinlogs_properties_app_id_values,
+    Esql.azure_signinlogs_properties_app_display_name_values,
+    Esql.azure_signinlogs_properties_authentication_requirement_values,
+    Esql.azure_signinlogs_properties_authentication_protocol_values,
+    Esql.azure_signinlogs_properties_client_app_used_values,
+    Esql.azure_signinlogs_properties_client_credential_type_values,
+    Esql.azure_signinlogs_properties_conditional_access_status_values,
+    Esql.azure_signinlogs_properties_correlation_id_values,
+    Esql.azure_signinlogs_properties_is_interactive_values,
+    Esql.azure_signinlogs_properties_mfa_detail_auth_method_values,
+    Esql.azure_signinlogs_properties_resource_display_name_values,
+    Esql.azure_signinlogs_properties_resource_id_values,
+    Esql.azure_signinlogs_properties_risk_state_values,
+    Esql.azure_signinlogs_properties_risk_detail_values,
+    Esql.azure_signinlogs_properties_status.error_code_values,
+    Esql.azure_signinlogs_properties_original_request_id_values,
+    Esql.user_id_values
 '''