splunk-security_content/detections/endpoint/w3wp_spawning_shell.yml

name: W3WP Spawning Shell
id: 0f03423c-7c6a-11eb-bc47-acde48001122
version: 3
date: '2024-05-16'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic identifies instances where a shell (PowerShell.exe
  or Cmd.exe) is spawned from W3WP.exe, the IIS worker process. This detection leverages
  data from Endpoint Detection and Response (EDR) agents, focusing on process creation
  events where the parent process is W3WP.exe. This activity is significant as it
  may indicate webshell activity, often associated with exploitation attempts like
  those by the HAFNIUM Group on Exchange servers. If confirmed malicious, this behavior
  could allow attackers to execute arbitrary commands, potentially leading to system
  compromise, data exfiltration, or further lateral movement within the network.
data_source:
- Sysmon EventID 1
search: '| tstats `security_content_summariesonly` count values(Processes.process_name)
  as process_name values(Processes.process) as process min(_time) as firstTime max(_time)
  as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name=w3wp.exe
  AND `process_cmd` OR `process_powershell` by Processes.dest Processes.parent_process
  Processes.original_file_name Processes.user | `drop_dm_object_name(Processes)` |
  `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| `w3wp_spawning_shell_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: Baseline your environment before production. It is possible
  build systems using IIS will spawn cmd.exe to perform a software build. Filter as
  needed.
references:
- https://www.microsoft.com/security/blog/2020/02/04/ghost-in-the-shell-investigating-web-shell-attacks/
- https://www.zerodayinitiative.com/blog/2021/8/17/from-pwn2own-2021-a-new-attack-surface-on-microsoft-exchange-proxyshell
- https://www.youtube.com/watch?v=FC6iHw258RI
- https://www.huntress.com/blog/rapid-response-microsoft-exchange-servers-still-vulnerable-to-proxyshell-exploit#what-should-you-do
tags:
  analytic_story:
  - ProxyNotShell
  - Data Destruction
  - ProxyShell
  - Hermetic Wiper
  - CISA AA22-257A
  - HAFNIUM Group
  - BlackByte Ransomware
  - CISA AA22-264A
  - Flax Typhoon
  - WS FTP Server Critical Vulnerabilities
  asset_type: Endpoint
  confidence: 80
  cve:
  - CVE-2021-34473
  - CVE-2021-34523
  - CVE-2021-31207
  impact: 70
  message: Possible Web Shell execution on $dest$
  mitre_attack_id:
  - T1505
  - T1505.003
  observable:
  - name: dest
    type: Endpoint
    role:
    - Victim
  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/T1505.003/windows-sysmon.log
    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
    sourcetype: xmlwineventlog