Detection: Windows Registry Certificate Added

Description

The following analytic detects the installation of a root CA certificate by monitoring specific registry paths for SetValue events. It leverages data from the Endpoint datamodel, focusing on registry paths containing "certificates" and registry values named "Blob." This activity is significant because unauthorized root CA certificates can compromise the integrity of encrypted communications and facilitate man-in-the-middle attacks. If confirmed malicious, this could allow an attacker to intercept, decrypt, or manipulate sensitive data, leading to severe security breaches.

1
2| tstats `security_content_summariesonly` count from datamodel=Endpoint.Registry where Registry.registry_path IN ("*\\certificates\\*") AND Registry.registry_value_name="Blob" by _time span=1h Registry.dest Registry.user Registry.registry_path Registry.registry_value_name Registry.process_guid Registry.registry_key_name Registry.registry_value_data 
3| `drop_dm_object_name(Registry)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_registry_certificate_added_filter`

Data Source

Name Platform Sourcetype Source Supported App
Sysmon EventID 12 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' N/A

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_registry_certificate_added_filter search *
windows_registry_certificate_added_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
T1553.004 Install Root Certificate Defense Evasion
T1553 Subvert Trust Controls Defense Evasion
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
Axiom

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

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes and Registry node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

False positives will be limited to a legitimate business applicating consistently adding new root certificates to the endpoint. Filter by user, process, or thumbprint.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A root certificate was added on $dest$. 42 60 70
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 XmlWinEventLog:Microsoft-Windows-Sysmon/Operational xmlwineventlog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational xmlwineventlog

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: 3