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Description

The following analytic identifies the execution of risky SPL commands with abnormally long run times by leveraging a machine learning model named "risky_command_abuse." It uses the Splunk Audit data model to compare current search activities against a baseline of the past seven days. This activity is significant for a SOC as it can indicate potential misuse or abuse of powerful SPL commands, which could lead to unauthorized data access or system manipulation. If confirmed malicious, this activity could allow an attacker to execute arbitrary scripts, delete data, or exfiltrate sensitive information.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Splunk_Audit
  • Last Updated: 2024-05-15
  • Author: Abhinav Mishra, Kumar Sharad and Xiao Lin, Splunk
  • ID: 19d0146c-2eae-4e53-8d39-1198a78fa9ca

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1059 Command and Scripting Interpreter Execution
Kill Chain Phase
  • Installation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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| tstats sum(Search_Activity.total_run_time) AS run_time, values(Search_Activity.search) as searches, count FROM datamodel=Splunk_Audit.Search_Activity WHERE (Search_Activity.user!="") AND (Search_Activity.total_run_time>1) AND (earliest=-1h@h latest=now) AND (Search_Activity.search IN ("*
| runshellscript *", "*
| collect *","*
| delete *", "*
| fit *", "*
| outputcsv *", "*
| outputlookup *", "*
| run *", "*
| script *", "*
| sendalert *", "*
| sendemail *", "*
| tscolle*")) AND (Search_Activity.search_type=adhoc) AND (Search_Activity.user!=splunk-system-user) BY _time, Search_Activity.user span=1h 
| apply risky_command_abuse 
| fields _time, Search_Activity.user, searches, run_time, IsOutlier(run_time) 
| rename IsOutlier(run_time) as isOutlier, _time as timestamp 
| where isOutlier>0.5 
| `splunk_command_and_scripting_interpreter_risky_spl_mltk_filter`

Macros

The SPL above uses the following Macros:

:information_source: splunk_command_and_scripting_interpreter_risky_spl_mltk_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Search_Activity.search
  • Search_Activity.total_run_time
  • Search_Activity.user
  • Search_Activity.search_type

How To Implement

This detection depends on MLTK app which can be found here - https://splunkbase.splunk.com/app/2890/ and the Splunk Audit datamodel which can be found here - https://splunkbase.splunk.com/app/1621/. Baseline model needs to be built using "Splunk Command and Scripting Interpreter Risky SPL MLTK Baseline" before this search can run. Please note that the current search only finds matches exactly one space between separator bar and risky commands.

Known False Positives

If the run time of a search exceeds the boundaries of outlier defined by the fitted density function model, false positives can occur, incorrectly labeling a long running search as potentially risky.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
20.0 50 40 Abnormally long run time for risk SPL command seen by user- [$Search_Activity.user$]

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 2