M365 or Entra ID Identity Sign-in from a Suspicious Source

  1[metadata]
  2creation_date = "2025/04/29"
  3integration = ["azure", "o365"]
  4maturity = "production"
  5updated_date = "2026/05/22"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10This rule correlate Entra-ID or Microsoft 365 mail successful sign-in events with network security alerts by source address.
 11Adversaries may trigger some network security alerts such as reputation or other anomalies before accessing cloud
 12resources.
 13"""
 14false_positives = [
 15    """
 16    Custom network security rules that triggers on a proxy or gateway used by users to access Azure or O365.
 17    """,
 18]
 19from = "now-8h"
 20interval="1h"
 21language = "esql"
 22license = "Elastic License v2"
 23name = "M365 or Entra ID Identity Sign-in from a Suspicious Source"
 24note = """## Triage and analysis
 25
 26### Investigating M365 or Entra ID Identity Sign-in from a Suspicious Source
 27
 28#### Possible investigation steps
 29
 30- Investiguate all the alerts associated with the source.ip.
 31  - Verify the network security alert details associated with this source.ip.
 32  - Verify all sign-in events associated with this source.ip.
 33  - Consider the source IP address and geolocation for the involved user account.
 34  - Consider the device used to sign in. Is it registered and compliant?
 35- Investigate other alerts associated with the user account during the past 48 hours.
 36- Contact the account owner and confirm whether they are aware of this activity.
 37- Check if this operation was approved and performed according to the organization's change management policy.
 38- If you suspect the account has been compromised, scope potentially compromised assets by tracking servers, services, and data accessed by the account in the last 24 hours.
 39
 40### Response and remediation
 41
 42- Initiate the incident response process based on the outcome of the triage.
 43- Disable or limit the account during the investigation and response.
 44- Identify the possible impact of the incident and prioritize accordingly; the following actions can help you gain context:
 45    - Identify the account role in the cloud environment.
 46    - Assess the criticality of affected services and servers.
 47    - Work with your IT team to identify and minimize the impact on users.
 48    - Identify if the attacker is moving laterally and compromising other accounts, servers, or services.
 49    - Identify any regulatory or legal ramifications related to this activity.
 50- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords or delete API keys as needed to revoke the attacker's access to the environment. Work with your IT teams to minimize the impact on business operations during these actions.
 51- Check if unauthorized new users were created, remove unauthorized new accounts, and request password resets for other IAM users.
 52- Consider enabling multi-factor authentication for users.
 53- Follow security best practices [outlined](https://docs.microsoft.com/en-us/azure/security/fundamentals/identity-management-best-practices) by Microsoft.
 54- Determine the initial vector abused by the attacker and take action to prevent reinfection via the same vector.
 55- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
 56
 57## Setup
 58
 59The Azure Fleet integration, Office 365 Logs Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule."""
 60risk_score = 73
 61rule_id = "f0cc239b-67fa-46fc-89d4-f861753a40f5"
 62severity = "high"
 63tags = [
 64    "Domain: Cloud",
 65    "Domain: SaaS",
 66    "Data Source: Azure",
 67    "Data Source: Entra ID",
 68    "Data Source: Entra ID Sign-in Logs",
 69    "Data Source: Microsoft 365",
 70    "Data Source: Microsoft 365 Audit Logs",
 71    "Use Case: Identity and Access Audit",
 72    "Use Case: Threat Detection",
 73    "Tactic: Initial Access",
 74    "Resources: Investigation Guide",
 75    "Rule Type: Higher-Order Rule",
 76]
 77timestamp_override = "event.ingested"
 78type = "esql"
 79
 80query = '''
 81from logs-o365.audit-*, logs-azure.signinlogs-*, .alerts-security.*
 82// filter for azure or m365 sign-in and external alerts with source.ip not null
 83| where to_ip(source.ip) is not null
 84  and (data_stream.dataset in ("o365.audit", "azure.signinlogs") or kibana.alert.rule.rule_id == "eb079c62-4481-4d6e-9643-3ca499df7aaa")
 85  and not cidr_match(
 86    to_ip(source.ip),
 87    "10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.0.0.0/24", "192.0.0.0/29",
 88    "192.0.0.8/32", "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24",
 89    "192.31.196.0/24", "192.52.193.0/24", "192.168.0.0/16", "192.88.99.0/24", "224.0.0.0/4",
 90    "100.64.0.0/10", "192.175.48.0/24", "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24",
 91    "240.0.0.0/4", "::1", "FE80::/10", "FF00::/8"
 92  )
 93
 94// capture relevant raw fields
 95| keep source.ip, event.action, event.outcome, data_stream.dataset, kibana.alert.rule.rule_id, event.category
 96
 97// classify each source ip based on alert type
 98| eval
 99  Esql.source_ip_mail_access_case = case(data_stream.dataset == "o365.audit" and event.action == "MailItemsAccessed" and event.outcome == "success", to_ip(source.ip)),
100  Esql.source_ip_azure_signin_case = case(data_stream.dataset == "azure.signinlogs" and event.outcome == "success", to_ip(source.ip)),
101  Esql.source_ip_network_alert_case = case(kibana.alert.rule.rule_id == "eb079c62-4481-4d6e-9643-3ca499df7aaa" and not data_stream.dataset in ("o365.audit", "azure.signinlogs"), to_ip(source.ip))
102
103// aggregate by source ip
104| stats
105    Esql.event_count = count(*),
106    Esql.source_ip_mail_access_case_count_distinct = count_distinct(Esql.source_ip_mail_access_case),
107    Esql.source_ip_azure_signin_case_count_distinct = count_distinct(Esql.source_ip_azure_signin_case),
108    Esql.source_ip_network_alert_case_count_distinct = count_distinct(Esql.source_ip_network_alert_case),
109    Esql.data_stream_dataset_count_distinct = count_distinct(data_stream.dataset),
110    Esql.data_stream_dataset_values = values(data_stream.dataset),
111    Esql.kibana_alert_rule_id_values = values(kibana.alert.rule.rule_id),
112    Esql.event_category_values = values(event.category)
113  by Esql.source_ip = to_ip(source.ip)
114
115// correlation condition
116| where
117  Esql.source_ip_network_alert_case_count_distinct > 0
118  and Esql.data_stream_dataset_count_distinct >= 2
119  and (Esql.source_ip_mail_access_case_count_distinct > 0 or Esql.source_ip_azure_signin_case_count_distinct > 0)
120  and Esql.event_count <= 100
121'''
122
123
124[[rule.threat]]
125framework = "MITRE ATT&CK"
126[[rule.threat.technique]]
127id = "T1078"
128name = "Valid Accounts"
129reference = "https://attack.mitre.org/techniques/T1078/"
130
131
132[rule.threat.tactic]
133id = "TA0001"
134name = "Initial Access"
135reference = "https://attack.mitre.org/tactics/TA0001/"