LoFP / rapid authentication from the same user using more than 5 different user agents and 3 application ids is highly unlikely under normal circumstances. however, there are potential scenarios that could lead to false positives.

Techniques

• T1078

Sample rules

Azure AD Multiple AppIDs and UserAgents Authentication Spike

• source: splunk
• technicques:
  • T1078

Description

The following analytic detects unusual authentication activity in Azure AD, specifically when a single user account has over 8 authentication attempts using 3+ unique application IDs and 5+ unique user agents within a short period. It leverages Azure AD audit logs, focusing on authentication events and using statistical thresholds. This behavior is significant as it may indicate an adversary probing for MFA requirements. If confirmed malicious, it suggests a compromised account, potentially leading to further exploitation, lateral movement, and data exfiltration. Early detection is crucial to prevent substantial harm.

Detection logic

`azure_monitor_aad` category=SignInLogs operationName="Sign-in activity" (properties.authenticationRequirement="multiFactorAuthentication" properties.status.additionalDetails="MFA required in Azure AD") OR (properties.authenticationRequirement=singleFactorAuthentication "properties.authenticationDetails{}.succeeded"=true) 
| bucket span=5m _time 
| rename properties.* as * 
| rename userAgent as user_agent 
| fillnull 
| stats count dc(appId) as unique_app_ids dc(user_agent) as unique_user_agents min(_time) as firstTime max(_time) as lastTime values(dest) as dest values(user_agent) as user_agent by user src vendor_account vendor_product signature 
| where count > 5 and unique_app_ids > 2 and unique_user_agents > 5 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `azure_ad_multiple_appids_and_useragents_authentication_spike_filter`

O365 Multiple AppIDs and UserAgents Authentication Spike

• source: splunk
• technicques:
  • T1078

Description

The following analytic identifies unusual authentication activity in an O365 environment, where a single user account experiences more than 8 authentication attempts using 3 or more unique application IDs and over 5 unique user agents within a short timeframe. It leverages O365 audit logs, focusing on authentication events and applying statistical thresholds. This behavior is significant as it may indicate an adversary probing for multi-factor authentication weaknesses. If confirmed malicious, it suggests a compromised account, potentially leading to unauthorized access, privilege escalation, and data exfiltration. Early detection is crucial to prevent further exploitation.

Detection logic

`o365_management_activity` Workload=AzureActiveDirectory (Operation=UserLoggedIn OR Operation=UserLoginFailed) 
| bucket span=5m _time 
| stats dc(_raw) as failed_attempts dc(ApplicationId) as unique_app_ids dc(UserAgent) as unique_user_agents values(ApplicationId) values(OS) values(signature) as signature by _time user src vendor_account vendor_product dest 
| where failed_attempts > 5 and unique_user_agents > 5 and unique_app_ids > 2 
| `o365_multiple_appids_and_useragents_authentication_spike_filter`