Detection: Splunk Digital Certificates Lack of Encryption

Updated Date: 2024-05-18 ID: 386a7ebc-737b-48cf-9ca8-5405459ed508 Author: Lou Stella, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic identifies Splunk forwarder connections that are not using TLS encryption. It leverages data from the splunkd logs, specifically looking for connections where the ssl field is set to "false". This activity is significant because unencrypted connections can expose sensitive data and allow unauthorized access, posing a security risk. If confirmed malicious, an attacker could exploit this vulnerability to download or publish forwarder bundles, potentially leading to arbitrary code execution and further compromise of the environment.

1`splunkd` group="tcpin_connections" ssl="false" 
2| stats values(sourceIp) latest(fwdType) latest(version) by hostname 
3| `splunk_digital_certificates_lack_of_encryption_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_digital_certificates_lack_of_encryption_filter search *
splunk_digital_certificates_lack_of_encryption_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
T1587.003 Digital Certificates Resource Development
KillChainPhase.WEAPONIZATION
NistCategory.DE_AE
Cis18Value.CIS_10
APT29
PROMETHIUM

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 True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

This anomaly search looks for forwarder connections that are not currently using TLS. It then presents the source IP, the type of forwarder, and the version of the forwarder. You can also remove the "ssl=false" argument from the initial stanza in order to get a full list of all your forwarders that are sending data, and the version of Splunk software they are running, for audit purposes. 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

None at this time

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
$hostname$ is not using TLS when forwarding data 20 25 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/metrics.log splunkd
Integration ✅ Passing Dataset /opt/splunk/var/log/splunk/metrics.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