LoFP / a source ip failing to authenticate with multiple users in a short period of time is not common legitimate behavior.

Techniques

• T1110
• T1110.003
• T1110.004
• T1586
• T1586.003

Sample rules

Okta Multiple Users Failing To Authenticate From Ip

• source: splunk
• technicques:
  • T1110.003

Description

The following analytic identifies instances where more than 10 unique user accounts have failed to authenticate from a single IP address within a 5-minute window in an Okta tenant. This detection uses OktaIm2 logs ingested via the Splunk Add-on for Okta Identity Cloud. Such activity is significant as it may indicate brute-force attacks or password spraying attempts. If confirmed malicious, this behavior suggests an external entity is attempting to compromise multiple user accounts, potentially leading to unauthorized access to organizational resources and data breaches.

Detection logic

| tstats `security_content_summariesonly` count max(_time) as lastTime, min(_time) as firstTime dc(Authentication.user) as unique_accounts values(Authentication.signature) as signature values(Authentication.user) as user values(Authentication.app) as app values(Authentication.authentication_method) as authentication_method from datamodel=Authentication where Authentication.action="failure" AND Authentication.signature=user.session.start by _time span=5m Authentication.src sourcetype 
| where unique_accounts > 9 
| `drop_dm_object_name("Authentication")` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `okta_multiple_users_failing_to_authenticate_from_ip_filter`

O365 Multiple Users Failing To Authenticate From Ip

• source: splunk
• technicques:
  • T1586
  • T1586.003
  • T1110
  • T1110.003
  • T1110.004

Description

The following analytic identifies instances where more than 10 unique user accounts fail to authenticate from a single IP address within a 5-minute window. This detection leverages O365 audit logs, specifically Azure Active Directory login failures (AzureActiveDirectoryStsLogon). Such activity is significant as it may indicate brute-force attacks or password spraying attempts. If confirmed malicious, this behavior suggests an external entity is attempting to breach security by targeting multiple accounts, potentially leading to unauthorized access. Immediate action is required to block or monitor the suspicious IP and notify affected users to enhance their security measures.

Detection logic

`o365_management_activity` Workload=AzureActiveDirectory Operation=UserLoginFailed ErrorNumber=50126 
|  bucket span=5m _time 
|  stats dc(user) as unique_accounts values(user) as user values(LogonError) as LogonError values(signature) as signature values(UserAgent) as UserAgent by _time, src_ip 
|  where unique_accounts > 10 
| `o365_multiple_users_failing_to_authenticate_from_ip_filter`