Detection: Splunk RCE via External Lookup Copybuckets

Updated Date: 2024-07-01 ID: 8598f9de-bba8-42a4-8ef0-12e1adda4131 Author: Rod Soto, Chase Franklin Type: Hunting Product: Splunk Enterprise Security

Description

The following detection provides the ability to detect remote code execution attempts against a script named copybuckets present within the splunk_archiver application by calling this script as an external lookup.

1index=_internal sourcetype="splunk_archiver-too_small" *.csv 
2| rex field=_raw "Invoking command:\s(?<command>.*)" 
3| stats min(_time) as firstTime max(_time) as lastTime values(command) as command values(severity) as severity by host 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `splunk_rce_via_external_lookup_copybuckets_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
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
splunk_rce_via_external_lookup_copybuckets_filter search *
splunk_rce_via_external_lookup_copybuckets_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
T1210 Exploitation of Remote Services Lateral Movement
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
APT28
Dragonfly
Earth Lusca
FIN7
Fox Kitten
MuddyWater
Threat Group-3390
Tonto Team
Wizard Spider
menuPass

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

Requires access to internal indexes

Known False Positives

An operator must identify elements indicatives of command execution requests by looking at regex data being extracted from the log. Not all the requests will be malicious.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
Possible exploitation attempt against $host$ 80 80 100
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/splunk_archiver.log splunk_archiver-too_small
Integration ✅ Passing Dataset /opt/splunk/var/log/splunk/splunk_archiver.log splunk_archiver-too_small

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: 1