Detection: O365 Excessive SSO logon errors

Updated Date: 2024-05-17 ID: 8158ccc4-6038-11eb-ae93-0242ac130002 Author: Rod Soto, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects accounts experiencing a high number of Single Sign-On (SSO) logon errors. It leverages data from the o365_management_activity dataset, focusing on failed user login attempts with SSO errors. This activity is significant as it may indicate brute-force attempts or the hijacking/reuse of SSO tokens. If confirmed malicious, attackers could potentially gain unauthorized access to user accounts, leading to data breaches, privilege escalation, or further lateral movement within the organization.

1`o365_management_activity` Workload=AzureActiveDirectory LogonError=*Sso* Operation=UserLoginFailed 
2| stats count min(_time) as firstTime max(_time) as lastTime values(user) as user by  src_ip signature user_agent authentication_service action
3| where count >= 5 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `o365_excessive_sso_logon_errors_filter`

Data Source

Name Platform Sourcetype Source Supported App
O365 UserLoginFailed N/A 'o365:management:activity' 'o365' N/A

Macros Used

Name Value
o365_management_activity sourcetype=o365:management:activity
o365_excessive_sso_logon_errors_filter search *
o365_excessive_sso_logon_errors_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1556 Modify Authentication Process Credential Access
KillChainPhase.EXPLOITAITON
KillChainPhase.INSTALLATION
NistCategory.DE_AE
Cis18Value.CIS_10
FIN13

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

You must install splunk Microsoft Office 365 add-on. This search works with o365:management:activity

Known False Positives

Logon errors may not be malicious in nature however it may indicate attempts to reuse a token or password obtained via credential access attack.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Excessive number of SSO logon errors from $src_ip$ using UserAgent $user_agent$. 64 80 80
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset o365 o365:management:activity
Integration ✅ Passing Dataset o365 o365:management:activity

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 4