Detection: Splunk protocol impersonation weak encryption simplerequest

Date: 2024-05-23 ID: 839d12a6-b119-4d44-ac4f-13eed95412c8 Author: Rod Soto, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic identifies instances where Splunk's Python3 client libraries fail to validate SSL certificates properly. It leverages logs from splunk_python to detect when "simpleRequest SSL certificate validation is enabled without hostname verification." This activity is significant because improper SSL certificate validation can expose the system to man-in-the-middle attacks, allowing attackers to intercept or alter data. If confirmed malicious, this vulnerability could lead to unauthorized access, data breaches, and potential system compromise. Upgrading to Splunk version 9 and configuring TLS hostname validation is recommended to mitigate this risk.

1`splunk_python` "simpleRequest SSL certificate validation is enabled without hostname verification" 
2| stats count by host path 
3| `splunk_protocol_impersonation_weak_encryption_simplerequest_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
splunk_python index=_internal sourcetype=splunk_python
splunk_protocol_impersonation_weak_encryption_simplerequest_filter search *
splunk_protocol_impersonation_weak_encryption_simplerequest_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

Default Configuration

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

Setting Value
Enabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Risk Based Alerting False
This configuration file applies to all detections of type hunting.

Implementation

Must upgrade to Splunk version 9 and Configure TLS host name validation for Splunk Python modules 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 search tries to address validation of server and client certificates within Splunk infrastructure, it might produce results from accidental or unintended requests to port 8089.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Failed to validate certificate on $host$ 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/splunk/var/log/splunk/splunkd.log splunk_python
Integration ✅ Passing Dataset /opt/splunk/var/log/splunk/splunkd.log splunk_python

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