Suspicious Curl Network Connection

name: Suspicious Curl Network Connection
id: 3f613dc0-21f2-4063-93b1-5d3c15eef22f
version: 11
date: '2026-03-10'
author: Michael Haag, Splunk
status: experimental
type: TTP
description: The following analytic detects the use of the curl command contacting suspicious remote domains, such as s3.amazonaws.com, which is indicative of Command and Control (C2) activity or downloading further implants. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs and command-line arguments. This activity is significant as it may indicate the presence of MacOS adware or other malicious software attempting to establish persistence or exfiltrate data. If confirmed malicious, this could allow attackers to maintain control over the compromised system and deploy additional payloads.
data_source:
    - Sysmon EventID 1
    - Sysmon for Linux EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
    as lastTime from datamodel=Endpoint.Processes where Processes.process_name IN ("curl", "curl.exe")
    Processes.process IN ("*s3.amazonaws.com*")
    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)`
    | `suspicious_curl_network_connection_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.
references:
    - https://redcanary.com/blog/clipping-silver-sparrows-wings/
rba:
    message: Suspicious usage of curl on $dest$
    risk_objects:
        - field: user
          type: user
          score: 50
        - field: dest
          type: system
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - Silver Sparrow
        - Ingress Tool Transfer
        - Linux Living Off The Land
        - APT37 Rustonotto and FadeStealer
        - GhostRedirector IIS Module and Rungan Backdoor
        - Hellcat Ransomware
    asset_type: Endpoint
    mitre_attack_id:
        - T1105
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint