tuning 'Microsoft Entra ID High Risk Sign-in' (#4739)

Author: terrancedejesus

rules/integrations/azure/initial_access_azure_active_directory_high_risk_signin.toml

@@ -0,0 +1,96 @@
+[metadata]
+creation_date = "2021/01/04"
+integration = ["azure"]
+maturity = "production"
+updated_date = "2025/05/21"
+
+[rule]
+author = ["Elastic", "Willem D'Haese"]
+description = """
+Identifies high risk Microsoft Entra ID sign-ins by leveraging Microsoft's Identity Protection machine learning
+and heuristics. Identity Protection categorizes risk into three tiers: low, medium, and high. While Microsoft does not
+provide specific details about how risk is calculated, each level brings higher confidence that the user or sign-in is
+compromised.
+"""
+from = "now-9m"
+index = ["filebeat-*", "logs-azure.signinlogs*"]
+language = "kuery"
+license = "Elastic License v2"
+name = "Microsoft Entra ID High Risk Sign-in"
+note = """## Triage and analysis
+
+### Investigating Microsoft Entra ID High Risk Sign-in
+
+This rule detects high-risk sign-ins in Microsoft Entra ID as identified by Identity Protection. These sign-ins are flagged with a risk level of `high` during the authentication process, indicating a strong likelihood of compromise based on Microsoft’s machine learning and heuristics. This alert is valuable for identifying accounts under active attack or compromise using valid credentials.
+
+### Possible investigation steps
+
+- Review the `azure.signinlogs.properties.user_id` and associated identity fields to determine the impacted user.
+- Inspect the `risk_level_during_signin` field and confirm it is set to `high`. If `risk_level_aggregated` is also present and high, this suggests sustained risk across multiple sign-ins.
+- Check `source.ip`, `source.geo.country_name`, and `source.as.organization.name` to evaluate the origin of the sign-in attempt. Flag unexpected geolocations or ASNs (e.g., anonymizers or residential ISPs).
+- Review the `device_detail` fields such as `operating_system` and `browser` for new or unrecognized devices.
+- Validate the `client_app_used` (e.g., legacy protocols, desktop clients) and `app_display_name` (e.g., Office 365 Exchange Online) to assess if risky legacy methods were involved.
+- Examine `applied_conditional_access_policies` to verify if MFA or blocking policies were triggered or bypassed.
+- Check `authentication_details.authentication_method` to see if multi-factor authentication was satisfied (e.g., "Mobile app notification").
+- Correlate this activity with other alerts or sign-ins from the same account within the last 24–48 hours.
+- Contact the user to confirm if the sign-in was expected. If not, treat the account as compromised and proceed with containment.
+
+### False positive analysis
+
+- Risky sign-ins may be triggered during legitimate travel, VPN use, or remote work scenarios from unusual locations.
+- In some cases, users switching devices or networks rapidly may trigger high-risk scores.
+- Automated scanners or penetration tests using known credentials may mimic high-risk login behavior.
+- Confirm whether the risk was remediated automatically by Microsoft Identity Protection before proceeding with escalations.
+
+### Response and remediation
+
+- If compromise is suspected, immediately disable the user account and revoke active sessions and tokens.
+- Initiate credential reset and ensure multi-factor authentication is enforced.
+- Review audit logs and sign-in history for the account to assess lateral movement or data access post sign-in.
+- Inspect activity on services such as Exchange, SharePoint, or Azure resources to understand the impact.
+- Determine if the attacker leveraged other accounts or escalated privileges.
+- Use the incident findings to refine conditional access policies, such as enforcing MFA for high-risk sign-ins or blocking legacy protocols.
+- Review and tighten policies that allow sign-ins from high-risk geographies or unknown devices.
+"""
+references = [
+    "https://docs.microsoft.com/en-us/azure/active-directory/conditional-access/howto-conditional-access-policy-risk",
+    "https://docs.microsoft.com/en-us/azure/active-directory/identity-protection/overview-identity-protection",
+    "https://docs.microsoft.com/en-us/azure/active-directory/identity-protection/howto-identity-protection-investigate-risk",
+]
+risk_score = 73
+rule_id = "37994bca-0611-4500-ab67-5588afe73b77"
+severity = "high"
+tags = [
+    "Domain: Cloud",
+    "Data Source: Azure",
+    "Data Source: Microsoft Entra ID",
+    "Data Source: Microsoft Entra ID Sign-in Logs",
+    "Use Case: Identity and Access Audit",
+    "Resources: Investigation Guide",
+    "Tactic: Initial Access",
+]
+timestamp_override = "event.ingested"
+type = "query"
+
+query = '''
+event.dataset:azure.signinlogs and
+  (
+    azure.signinlogs.properties.risk_level_during_signin:high or
+    azure.signinlogs.properties.risk_level_aggregated:high
+  )
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1078"
+name = "Valid Accounts"
+reference = "https://attack.mitre.org/techniques/T1078/"
+
+
+[rule.threat.tactic]
+id = "TA0001"
+name = "Initial Access"
+reference = "https://attack.mitre.org/tactics/TA0001/"
+