Cisco Secure Firewall - Wget or Curl Download

name: Cisco Secure Firewall - Wget or Curl Download
id: 173a1cb9-1814-4128-a9dc-f29dade89957
version: 9
creation_date: '2025-04-03'
modification_date: '2026-05-13'
author: Nasreddine Bencherchali, Splunk
status: production
type: Anomaly
description: |
    The following analytic detects outbound connections initiated by command-line tools such as curl or wget. It leverages Cisco Secure Firewall Threat Defense logs and identifies allowed connections (action=Allow) where either the EVE_Process or ClientApplication fields indicate use of these utilities. While curl and wget are legitimate tools commonly used for software updates and scripting, adversaries often abuse them to download payloads, retrieve additional tools, or establish staging infrastructure from compromised systems. If confirmed malicious, this behavior may indicate the download phase of an attack chain or a command-and-control utility retrieval.
data_source:
    - Cisco Secure Firewall Threat Defense Connection Event
search: |
    `cisco_secure_firewall` EventType=ConnectionEvent action IN ("Trust", "Allow", "allowed") AND
    ( EVE_Process IN ("*curl*", "*wget*") OR ClientApplication IN ("cURL", "Wget") )
    | stats count min(_time) as firstTime max(_time) as lastTime
        Values(rule) as rule
        Values(url) as url
        Values(dest_port) as dest_port
        Values(ClientApplicationVersion) as ClientApplicationVersion
        Values(src_port) as src_port
        by src, dest, transport, EVE_Process, ClientApplication, action
    | table src src_port dest dest_port transport url EVE_Process ClientApplication ClientApplicationVersion rule firstTime lastTime
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `cisco_secure_firewall___wget_or_curl_download_filter`
how_to_implement: |
    This search requires Cisco Secure Firewall Threat Defense Logs, which
    includes the ConnectionEvent EventType. This search uses an input macro named `cisco_secure_firewall`.
    We strongly recommend that you specify your environment-specific configurations
    (index, source, sourcetype, etc.) for Cisco Secure Firewall Threat Defense logs. Replace the macro definition
    with configurations for your Splunk environment. The search also uses a post-filter
    macro designed to filter out known false positives.
    The logs are to be ingested using the Splunk Add-on for Cisco Security Cloud (https://splunkbase.splunk.com/app/7404).
    The access policy must also enable logging.
known_false_positives: |
    Developers, administrators, or automation tools may use `curl` or `wget` for legitimate purposes such as software installation, configuration scripts, or CI/CD tasks.
    Security tools or health monitoring scripts may also use these utilities to check service availability or download updates.
    Review the destination `url`, frequency, and process context to validate whether the download activity is authorized.
references:
    - https://www.cisco.com/c/en/us/td/docs/security/firepower/741/api/FQE/secure_firewall_estreamer_fqe_guide_740.pdf
drilldown_searches:
    - name: View the detection results for - "$src$"
      search: '%original_detection_search% | search  src = "$src$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$src$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$") | 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"
intermediate_findings:
    entities:
        - field: src
          type: system
          score: 20
          message: The process $EVE_Process$ initiated an allowed connection to download content using a command-line utility ($ClientApplication$) from $url$. This behavior may indicate tool staging or payload retrieval via curl or wget.
threat_objects:
    - field: EVE_Process
      type: process_name
    - field: url
      type: url
analytic_story:
    - Cisco Secure Firewall Threat Defense Analytics
asset_type: Network
mitre_attack_id:
    - T1053.003
    - T1059
    - T1071.001
    - T1105
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_secure_firewall_threat_defense/connection_event/connection_events.log
          source: not_applicable
          sourcetype: cisco:sfw:estreamer
      test_type: unit