Splunk User Enumeration Attempt

SPLUNK detection rule by Lou Stella, Splunk · Apache-2.0

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.

name: Splunk User Enumeration Attempt
id: 25625cb4-1c4d-4463-b0f9-7cb462699cde
version: 9
creation_date: '2022-04-29'
modification_date: '2026-05-14'
author: Lou Stella, Splunk
status: production
type: TTP
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.
data_source:
    - Splunk
search: '`splunkd_failed_auths` | stats count(user) as auths by user, src | where auths>5 | stats values(user) as user, sum(auths) as TotalFailedAuths by src | `splunk_user_enumeration_attempt_filter`'
how_to_implement: 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known_false_positives: Automation executing authentication attempts against your Splunk infrastructure with outdated credentials may cause false positives.
references:
    - https://www.splunk.com/en_us/product-security/announcements/svd-2022-0502.html
drilldown_searches:
    - name: View the detection results for $user$
      search: '%original_detection_search% | search  user = $user$'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for $user$
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ($user$) starthoursago=168 endhoursago=1 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
finding:
    title: $TotalFailedAuths$ failed authentication events to Splunk from $src$ detected.
    entity:
        field: user
        type: user
        score: 40
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Splunk Vulnerabilities
asset_type: Endpoint
cve:
    - CVE-2021-33845
mitre_attack_id:
    - T1078
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: application
security_domain: access
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1078/splunkd_auth/audittrail.log
          source: audittrail
          sourcetype: audittrail
          index: _audit
      test_type: unit

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Executable code, not a declarative rule

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