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Description

The following analytic detects programs that have been started by pcalua.exe. pcalua.exe is the Microsoft Windows Program Compatability Assistant. While this tool can be used to start legitimate programs, it has been observed being used to evade protections on command line execution.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-04-05
  • Author: Eric McGinnis, Splunk
  • ID: 3428ac18-a410-4823-816c-ce697d26f7a8

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1202 Indirect Command Execution Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 8
  • CIS 10
CVE
1
2
3
4
5
6
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process="*pcalua* -a*" by Processes.dest Processes.user Processes.parent_process Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.process_path 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_indirect_command_execution_via_pcalua_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_indirect_command_execution_via_pcalua_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.dest
  • Processes.user
  • Processes.dest
  • Processes.user
  • Processes.parent_process
  • Processes.parent_process_name
  • Processes.process_name
  • Processes.process
  • Processes.process_id
  • Processes.parent_process_id
  • Processes.process_path

How To Implement

To successfully implement this search, you need to be ingesting logs with the full process path in the process field of CIM's Process data model. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances where pcalua.exe may be used.

Known False Positives

Some legacy applications may be run using pcalua.exe. Filter these results as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 The Program Compatability Assistant (pcalua.exe) launched the process $process_name$

: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: 1