Detection: Splunk User Enumeration Attempt

Updated Date: 2025-05-02 ID: 25625cb4-1c4d-4463-b0f9-7cb462699cde Author: Lou Stella, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies attempts to enumerate usernames in Splunk by detecting multiple failed authentication attempts from the same source. It leverages data from the _audit index, specifically focusing on failed authentication events. This activity is significant for a SOC because it can indicate an attacker trying to discover valid usernames, which is a precursor to more targeted attacks like password spraying or brute force attempts. If confirmed malicious, this activity could lead to unauthorized access, compromising the security of the Splunk environment and potentially exposing sensitive data.

1`splunkd_failed_auths` 
2| stats count(user) as auths by user, src 
3| where auths>5 
4| stats values(user) as user, sum(auths) as TotalFailedAuths by src 
5| `splunk_user_enumeration_attempt_filter`

Data Source

Name Platform Sourcetype Source
Splunk Splunk icon Splunk 'splunkd_ui_access' 'splunkd_ui_access.log'

Macros Used

Name Value
splunkd_failed_auths index=_audit "action=login attempt" "info=failed"
splunk_user_enumeration_attempt_filter search *
splunk_user_enumeration_attempt_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
T1078 Valid Accounts Defense Evasion
Delivery
Exploitation
Installation
DE.CM
CIS 10

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 Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

This detection does not require you to ingest any new data. The detection does require the ability to search the _audit index. This detection may assist in efforts to find password spraying or brute force authorization attempts in addition to someone enumerating usernames.

Known False Positives

Automation executing authentication attempts against your Splunk infrastructure with outdated credentials may cause false positives.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

$TotalFailedAuths$ failed authentication events to Splunk from $src$ detected.

Risk Object Risk Object Type Risk Score Threat Objects
user user 40 src

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset audittrail audittrail
Integration ✅ Passing Dataset audittrail audittrail

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: 8