adding new detection

detections/cloud/o365_high_number_of_failed_authentications_for_user.yml

@@ -0,0 +1,50 @@
+name: O365 High Number Of Failed Authentications for User
+id: 31641378-2fa9-42b1-948e-25e281cb98f7
+version: 1
+date: '2023-10-10'
+author: Mauricio Velazco, Splunk
+status: production
+type: TTP
+data_source: []
+description: The following analytic identifies an O365 account that has experienced more than 20 failed authentication events within a span of 5 minutes. This could be indicative of an attacker attempting to brute force or guess the password for that particular user account. It leverages the O365 Unified Audit Logs, specifically the "UserLoginFailed" events. By monitoring the frequency and volume of these events for individual users, the analytic can flag accounts that exceed the set threshold of failed attempts within the defined timeframe. Multiple failed login attempts in a short period can be a strong indicator of malicious activity. While there could be benign reasons, such as a user forgetting their password, the rapid succession of failed attempts is often a sign of an attacker trying to gain unauthorized access. By detecting and alerting on this behavior, the SOC can quickly investigate and take appropriate action, potentially stopping an attack in its early stages. Given that environments differ across organizations, security teams should consider customizing the threshold of this detection to better suit their specific needs and risk profile. If an attacker successfully guesses or brute-forces a user's password after numerous attempts, they can gain unauthorized access to the O365 environment. This unauthorized access could allow them to view sensitive emails, documents, and other data.
+search: ' `o365_management_activity` Operation=UserLoginFailed  record_type=AzureActiveDirectoryStsLogon app=AzureActiveDirectory
+  | bucket span=5m _time 
+  | stats  dc(_raw) AS failed_attempts  values(src_ip) by user, _time
+  | where failed_attempts > 10
+  | `o365_high_number_of_failed_authentications_for_user_filter`'
+how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
+known_false_positives: Although unusual, users who have lost their passwords may trigger this detection. Filter as needed.
+references:
+- https://attack.mitre.org/techniques/T1110/
+- https://attack.mitre.org/techniques/T1110/001/
+tags:
+  analytic_story:
+  - UPDATE_STORY_NAME
+  asset_type: O365 tenant
+  confidence: 70
+  impact: 50
+  message: User $user$ failed to authenticate more than 10 times in the span of 5 minutes.
+  mitre_attack_id:
+  - T1110
+  - T1110.001
+  observable:
+  - name: user
+    type: User
+    role:
+    - Victim
+  product:
+  - Splunk Enterprise
+  - Splunk Enterprise Security
+  - Splunk Cloud
+  risk_score: 35
+  required_fields:
+  - _time
+  - src_ip
+  - user
+  security_domain: identity
+tests:
+- name: True Positive Test
+  attack_data:
+  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1110.001/o365_high_number_authentications_for_user/o365_high_number_authentications_for_user.log
+    source: o365:management:activity
+    sourcetype: o365:management:activity