Linux Ingress Tool Transfer with Curl

name: Linux Ingress Tool Transfer with Curl
id: 8c1de57d-abc1-4b41-a727-a7a8fc5e0857
version: 12
date: '2026-03-10'
author: Michael Haag, Splunk
status: production
type: Anomaly
description: The following analytic detects the use of the curl command with specific switches (-O, -sO, -ksO, --output) commonly used to download remote scripts or binaries. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line arguments. This activity is significant as it may indicate an attempt to download and execute potentially malicious files, often used in initial stages of an attack. If confirmed malicious, this could lead to unauthorized code execution, enabling attackers to compromise the system further.
data_source:
    - Sysmon for Linux EventID 1
search: |
    | tstats `security_content_summariesonly`
      count min(_time) as firstTime
            max(_time) as lastTime

    from datamodel=Endpoint.Processes where

    Processes.process_name=curl
    Processes.process IN ("*-O*","*-sO*","*-ksO*","*--output*")
    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)`
    | where match(process, "(?i)(-O|-sO|-ksO|--output)")
    | `linux_ingress_tool_transfer_with_curl_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 will be present. Tune and then change type to TTP.
references:
    - https://gtfobins.github.io/gtfobins/curl/
    - https://curl.se/docs/manpage.html#-I
    - https://gtfobins.github.io/gtfobins/curl/
    - https://github.com/rapid7/metasploit-framework/search?q=curl
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 ("$user$", "$dest$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: An instance of $process_name$ was identified on endpoint $dest$ by user $user$ to download a remote file. Review activity for further details.
    risk_objects:
        - field: user
          type: user
          score: 20
        - field: dest
          type: system
          score: 20
    threat_objects:
        - field: process_name
          type: process_name
tags:
    analytic_story:
        - Ingress Tool Transfer
        - Linux Living Off The Land
        - XorDDos
        - NPM Supply Chain Compromise
    asset_type: Endpoint
    mitre_attack_id:
        - T1105
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1105/atomic_red_team/curl-linux-sysmon.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux