Windows Exfiltration Over C2 Via Invoke RestMethod

name: Windows Exfiltration Over C2 Via Invoke RestMethod
id: 06ade821-f6fa-40d0-80af-15bc1d45b3ba
version: 14
creation_date: '2023-04-05'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects potential data exfiltration using PowerShell's Invoke-RestMethod. It leverages PowerShell Script Block Logging to identify scripts that attempt to upload files via HTTP POST requests. This activity is significant as it may indicate an attacker is exfiltrating sensitive data, such as desktop screenshots or files, to an external command and control (C2) server. If confirmed malicious, this could lead to data breaches, loss of sensitive information, and further compromise of the affected systems. Immediate investigation is recommended to determine the intent and scope of the activity.
data_source:
    - Powershell Script Block Logging 4104
search: |-
    `powershell` EventCode=4104 ScriptBlockText = "*Invoke-RestMethod *" AND ScriptBlockText = "* -Uri *" AND ScriptBlockText = "* -Method *" AND ScriptBlockText = "* Post *" AND ScriptBlockText = "* -InFile *"
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY dest signature signature_id
           user_id vendor_product EventID
           Guid Opcode Name
           Path ProcessID ScriptBlockId
           ScriptBlockText
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `windows_exfiltration_over_c2_via_invoke_restmethod_filter`
how_to_implement: To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba.
known_false_positives: False positives should be limited. Filter as needed.
references:
    - https://twitter.com/_CERT_UA/status/1620781684257091584
    - https://cert.gov.ua/article/3761104
drilldown_searches:
    - name: View the detection results for - "$Computer$"
      search: '%original_detection_search% | search  Computer = "$Computer$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$Computer$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$Computer$") | 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"
finding:
    title: A PowerShell script on $dest$ is attempting to transfer files to a remote URL.
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Microsoft WSUS CVE-2025-59287
    - Hellcat Ransomware
    - APT37 Rustonotto and FadeStealer
    - Winter Vivern
    - Water Gamayun
asset_type: Endpoint
mitre_attack_id:
    - T1041
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/winter-vivern/pwh_exfiltration/windows-powershell-xml.log
          source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
          sourcetype: XmlWinEventLog
      test_type: unit