Detection: Splunk protocol impersonation weak encryption selfsigned

Updated Date: 2024-05-21 ID: c76c7a2e-df49-414a-bb36-dce2683770de Author: Rod Soto, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic identifies the use of Splunk's default self-signed certificates, which are flagged as insecure. It detects events from the splunkd log where the event message indicates that an X509 certificate should not be used. This activity is significant because using weak encryption and self-signed certificates can expose the system to man-in-the-middle attacks and other security vulnerabilities. If confirmed malicious, attackers could impersonate Splunk services, intercept sensitive data, and compromise the integrity of the Splunk environment.

1`splunkd` certificate event_message="X509 certificate* should not be used*" 
2| stats count by host CN component log_level 
3| `splunk_protocol_impersonation_weak_encryption_selfsigned_filter`

Data Source

Name Platform Sourcetype Source Supported App
Splunk Splunk icon Splunk 'splunkd_ui_access' 'splunkd_ui_access.log' N/A

Macros Used

Name Value
splunkd index=_internal sourcetype=splunkd
splunk_protocol_impersonation_weak_encryption_selfsigned_filter search *
splunk_protocol_impersonation_weak_encryption_selfsigned_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
T1588.004 Digital Certificates Resource Development
KillChainPhase.WEAPONIZATION
NistCategory.DE_AE
Cis18Value.CIS_10
BlackTech
Lazarus Group
LuminousMoth
Silent Librarian

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 False
This configuration file applies to all detections of type hunting.

Implementation

Must upgrade to Splunk version 9 and Configure TLS in order to apply this search. Splunk SOAR customers can find a SOAR workbook that walks an analyst through the process of running these hunting searches in the references list of this detection. In order to use this workbook, a user will need to run a curl command to post the file to their SOAR instance such as "curl -u username:password https://soar.instance.name/rest/rest/workbook_template -d @splunk_psa_0622.json". A user should then create an empty container or case, attach the workbook, and begin working through the tasks.

Known False Positives

This searches finds self signed certificates issued by Splunk which are not recommended from Splunk version 9 forward.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Splunk default issued certificate at $host$ 40 50 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 /opt/splun/var/log/splunk/splunkd.log splunkd
Integration ✅ Passing Dataset /opt/splun/var/log/splunk/splunkd.log splunkd

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: 2