Windows Curl Upload to Remote Destination

SPLUNK detection rule by Michael Haag, Splunk · Apache-2.0

The following analytic detects the use of Windows Curl.exe to upload a file to a remote destination. It identifies command-line arguments such as `-T`, `--upload-file`, `-d`, `--data`, and `-F` in process execution logs. This activity is significant because adversaries may use Curl to exfiltrate data or upload malicious payloads. If confirmed malicious, this could lead to data breaches or further compromise of the system. Analysts should review parallel processes and network logs to determine if the upload was successful and isolate the endpoint if necessary.

name: Windows Curl Upload to Remote Destination
id: 42f8f1a2-4228-11ec-aade-acde48001122
version: 18
creation_date: '2021-11-10'
modification_date: '2026-07-14'
author: Michael Haag, Splunk
status: production
type: TTP
description: |-
    The following analytic detects the use of Windows Curl.exe to upload a file to a remote destination.
    It identifies command-line arguments such as `-T`, `--upload-file`, `-d`, `--data`, and `-F` in process execution logs.
    This activity is significant because adversaries may use Curl to exfiltrate data or upload malicious payloads. If confirmed malicious, this could lead to data breaches or further compromise of the system.
    Analysts should review parallel processes and network logs to determine if the upload was successful and isolate the endpoint if necessary.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
    - Cisco Network Visibility Module Flow Data
search: |-
    | tstats `security_content_summariesonly`
      count min(_time) as firstTime
            max(_time) as lastTime

    from datamodel=Endpoint.Processes where

    (
        Processes.process_name=curl.exe
        OR
        Processes.original_file_name=Curl.exe
    )
    Processes.process IN (
        "*-T *",
        "*--upload-file *",
        "*-d *",
        "*--data *",
        "*-F *"
    )

    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)`
    | `windows_curl_upload_to_remote_destination_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: False positives may be limited to source control applications and may be required to be filtered out.
references:
    - https://everything.curl.dev/usingcurl/uploads
    - https://techcommunity.microsoft.com/t5/containers/tar-and-curl-come-to-windows/ba-p/382409
    - https://twitter.com/d1r4c/status/1279042657508081664?s=20
drilldown_searches:
    - name: View the detection results for - "$user$" and "$dest$"
      search: '%original_detection_search% | search  user = "$user$" dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | 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: An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ uploading a file to a remote destination.
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ uploading a file to a remote destination.
threat_objects:
    - field: parent_process_name
      type: parent_process_name
    - field: process_name
      type: process_name
analytic_story:
    - Cisco Network Visibility Module Analytics
    - Compromised Windows Host
    - Ingress Tool Transfer
    - Microsoft WSUS CVE-2025-59287
    - NPM Supply Chain Compromise
    - PromptLock
    - Axios Supply Chain Post Compromise
asset_type: Endpoint
mitre_attack_id:
    - T1105
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test - Sysmon
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1105/atomic_red_team/windows-sysmon_curl_upload.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit
    - name: True Positive Test - Cisco NVM
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_network_visibility_module/cisco_nvm_flowdata/nvm_flowdata.log
          source: not_applicable
          sourcetype: cisco:nvm:flowdata:v2
      test_type: unit

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74368695-7de6-4cdc-8419-e7d5a26fe27a

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