Windows PowerShell Process With Malicious String

SPLUNK detection rule by Steven Dick · Apache-2.0

The following analytic detects the execution of multiple offensive toolkits and commands through the process execution datamodel. This method captures commands given directly to powershell.exe, allowing for the identification of suspicious activities including several well-known tools used for credential theft, lateral movement, and persistence. If confirmed malicious, this could lead to unauthorized access, privilege escalation, and potential compromise of sensitive information within the environment.

name: Windows PowerShell Process With Malicious String
id: 5df35d50-e1a3-4a52-a337-92e69d9b1b8a
version: 9
creation_date: '2025-01-13'
modification_date: '2026-05-13'
author: Steven Dick
status: production
type: TTP
description: The following analytic detects the execution of multiple offensive toolkits and commands through the process execution datamodel. This method captures commands given directly to powershell.exe, allowing for the identification of suspicious activities including several well-known tools used for credential theft, lateral movement, and persistence. If confirmed malicious, this could lead to unauthorized access, privilege escalation, and potential compromise of sensitive information within the environment.
data_source:
    - Windows Event Log Security 4688
    - Sysmon EventID 1
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE `process_powershell`
      BY Processes.action Processes.dest Processes.original_file_name
         Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
         Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
         Processes.process Processes.process_exec Processes.process_guid
         Processes.process_hash Processes.process_id Processes.process_integrity_level
         Processes.process_name Processes.process_path Processes.user
         Processes.user_id Processes.vendor_product
    | `drop_dm_object_name(Processes)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | lookup malicious_powershell_strings command as process
    | where isnotnull(match)
    | `windows_powershell_process_with_malicious_string_filter`
how_to_implement: The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
known_false_positives: No false positives have been identified at this time. commands with overlap.
references:
    - https://attack.mitre.org/techniques/T1059/001/
    - https://github.com/PowerShellMafia/PowerSploit
    - https://github.com/PowerShellEmpire/
    - https://github.com/S3cur3Th1sSh1t/PowerSharpPack
drilldown_searches:
    - name: View the detection results for - "$dest$" and "$user$"
      search: '%original_detection_search% | search dest = "$dest$" AND user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$" and "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$","$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
    - name: Investigate PowerShell on $dest$
      search: '| from datamodel:Endpoint.Processes | search dest=$dest|s$ process_name=$process_name$ "*$match$*"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
finding:
    title: The user $user$ ran a known malicious PowerShell string matching *$match$* on $dest$
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: The user $user$ ran a known malicious PowerShell string matching *$match$* on $dest$
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Malicious PowerShell
asset_type: Endpoint
mitre_attack_id:
    - T1059.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1087.002/AD_discovery/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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