Windows Curl Download to Suspicious Path

name: Windows Curl Download to Suspicious Path
id: c32f091e-30db-11ec-8738-acde48001122
version: 21
creation_date: '2021-10-19'
modification_date: '2026-05-13'
author: Michael Haag, Nasreddine Bencherchali, Splunk
status: production
type: TTP
description: |
    The following analytic detects the use of Windows Curl.exe to download
    a file to a suspicious location, such as AppData, ProgramData, or Public directories.
    It leverages data from Endpoint Detection and Response (EDR) agents, focusing on
    command-line executions that include the -O or --output options. This activity is
    significant because downloading files to these locations can indicate an attempt
    to bypass security controls or establish persistence. If confirmed malicious, this
    behavior could lead to unauthorized code execution, data exfiltration, or further
    compromise of the system.
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 ("*-O *","*--output*", "*--output-dir*")
    Processes.process IN (
          "*:\\PerfLogs\\*",
          "*:\\Windows\\Temp\\*",
          "*\\AppData\\*",
          "*\\ProgramData\\*",
          "*\\Users\\Public\\*",
          "*%AppData%*",
          "*%Public%*",
          "*%Temp%*",
          "*%tmp%*"
          )
    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_download_to_suspicious_path_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: |
    It is possible Administrators or super users will use Curl for legitimate purposes. Filter as needed.
references:
    - https://thedfirreport.com/2021/10/18/icedid-to-xinglocker-ransomware-in-24-hours/
    - https://attack.mitre.org/techniques/T1105/
    - https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1105/T1105.md
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 $user$ to download a file to a suspicious directory.
    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 $user$ to download a file to a suspicious directory.
threat_objects:
    - field: parent_process_name
      type: parent_process_name
    - field: process_name
      type: process_name
analytic_story:
    - APT37 Rustonotto and FadeStealer
    - Black Basta Ransomware
    - China-Nexus Threat Activity
    - Cisco Network Visibility Module Analytics
    - Compromised Windows Host
    - Forest Blizzard
    - GhostRedirector IIS Module and Rungan Backdoor
    - IcedID
    - Ingress Tool Transfer
    - NPM Supply Chain Compromise
    - Salt Typhoon
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.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
      test_type: unit