Splunk User Enumeration Attempt

Description

On May 3rd, 2022, Splunk published a security advisory for username enumeration stemming from verbose login failure messages present on some REST endpoints. This detection will alert on attempted exploitation in patched versions of Splunk as well as actual exploitation in unpatched version of Splunk.

Type: TTP
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
Last Updated: 2022-04-29
Author: Lou Stella, Splunk
ID: 25625cb4-1c4d-4463-b0f9-7cb462699cde

Annotations

ATT&CK

ID	Technique	Tactic
T1078	Valid Accounts	Defense Evasion, Persistence, Privilege Escalation, Initial Access

Kill Chain Phase

Exploitation
Installation
Delivery

NIST

DE.CM

CIS20

CIS 10

CVE

ID	Summary	CVSS
CVE-2021-33845	The Splunk Enterprise REST API allows enumeration of usernames via the lockout error message. The potential vulnerability impacts Splunk Enterprise instances before 8.1.7 when configured to repress verbose login errors.	5.0

Search

 `splunkd_failed_auths` 
| stats count(user) as auths by user, src 
| where auths>5 
| stats values(user) as "Users", sum(auths) as TotalFailedAuths by src 
| `splunk_user_enumeration_attempt_filter`

Macros

The SPL above uses the following Macros:

splunkd_failed_auths

splunk_user_enumeration_attempt_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

user
src
info
action

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Automation executing authentication attempts against your Splunk infrastructure with outdated credentials may cause false positives.

Associated Analytic Story

Splunk Vulnerabilities

RBA

Risk Score	Impact	Confidence	Message
40.0	50	80	$TotalFailedAuths$ failed authentication events to Splunk from $src$ detected.

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

https://www.splunk.com/en_us/product-security/announcements/svd-2022-0502.html

Test Dataset

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 | version: 1

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