splunk-security_content/detections/endpoint/linux_proxy_socks_curl.yml

name: Linux Proxy Socks Curl
id: bd596c22-ad1e-44fc-b242-817253ce8b08
version: 3
date: '2024-08-14'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic detects the use of the `curl` command with proxy-related
  arguments such as `-x`, `socks`, `--preproxy`, and `--proxy`. This detection leverages
  data from Endpoint Detection and Response (EDR) agents, focusing on command-line
  executions and process details. This activity is significant as it may indicate
  an adversary attempting to use a proxy to evade network monitoring and obscure their
  actions. If confirmed malicious, this behavior could allow attackers to bypass security
  controls, making it difficult to track their activities and potentially leading
  to unauthorized data access or exfiltration.
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 ("*-x *", "*socks4a://*", "*socks5h://*", "*socks4://*","*socks5://*",
  "*--preproxy *", "--proxy*") by Processes.dest Processes.user Processes.parent_process_name
  Processes.process_name Processes.process Processes.process_id Processes.parent_process_id
  | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
  | `linux_proxy_socks_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 may be present based on proxy usage internally.
  Filter as needed.
references:
- https://www.offensive-security.com/metasploit-unleashed/proxytunnels/
- https://curl.se/docs/manpage.html
- https://en.wikipedia.org/wiki/SOCKS
- https://oxylabs.io/blog/curl-with-proxy
- https://reqbin.com/req/c-ddxflki5/curl-proxy-server#:~:text=To%20use%20a%20proxy%20with,be%20URL%20decoded%20by%20Curl.
- https://gtfobins.github.io/gtfobins/curl/
tags:
  analytic_story:
  - Linux Living Off The Land
  - Ingress Tool Transfer
  asset_type: Endpoint
  confidence: 80
  impact: 70
  message: An instance of $process_name$ was identified on endpoint $dest$ by user
    $user$ utilizing a proxy. Review activity for further details.
  mitre_attack_id:
  - T1090
  - T1095
  observable:
  - name: user
    type: User
    role:
    - Victim
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: process_name
    type: Process
    role:
    - Attacker
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.dest
  - Processes.user
  - Processes.parent_process_name
  - Processes.parent_process
  - Processes.original_file_name
  - Processes.process_name
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_path
  - Processes.process_path
  - Processes.parent_process_id
  risk_score: 56
  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
    update_timestamp: true