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Description

This search, detects execution of suspicious bash commands from various commonly leveraged bash scripts like (AutoSUID, LinEnum, LinPeas) to perform discovery of possible paths of privilege execution, password files, vulnerable directories, executables and file permissions on a Linux host.
The search logic specifically looks for high number of distinct commands run in a short period of time.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-12-06
  • Author: Bhavin Patel, Splunk
  • ID: 0edd5112-56c9-11ec-b990-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1059.004 Unix Shell Execution
Kill Chain Phase
  • Exploitation
NIST
CIS20
CVE 


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| tstats `security_content_summariesonly` count values(Processes.process) values(Processes.process_name) values(Processes.parent_process_name) dc(Processes.process) as distinct_commands dc(Processes.process_name) as distinct_process_names min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where [
|inputlookup linux_tool_discovery_process.csv 
| rename process as Processes.process 
|table Processes.process] by _time span=5m Processes.user Processes.dest 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| where distinct_commands > 40 AND distinct_process_names > 3
| `suspicious_linux_discovery_commands_filter`

Macros

The SPL above uses the following Macros:

:information_source: suspicious_linux_discovery_commands_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
  • Processes.process
  • Processes.parent_process_name
  • Processes.user
  • Processes.process_name

How To Implement

This detection search is based on Splunk add-on for Microsoft Sysmon-Linux.(https://splunkbase.splunk.com/app/6176/). Please install this add-on to parse fields correctly and execute detection search. Consider customizing the time window and threshold values according to your environment.

Known False Positives

Unless an administrator is using these commands to troubleshoot or audit a system, the execution of these commands should be monitored.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
81.0 90 90 Suspicious Linux Discovery Commands detected on $dest$

: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

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