name: W3WP Spawning Shell
id: 0f03423c-7c6a-11eb-bc47-acde48001122
version: 2
date: '2023-07-10'
author: Michael Haag, Splunk
status: production
type: TTP
description: This query identifies a shell, PowerShell.exe or Cmd.exe, spawning from
  W3WP.exe, or IIS. In addition to IIS logs, this behavior with an EDR product will
  capture potential webshell activity, similar to the HAFNIUM Group abusing CVEs,
  on publicly available Exchange mail servers. During triage, review the parent process
  and child process of the shell being spawned. Review the command-line arguments
  and any file modifications that may occur. Identify additional parallel process,
  child processes, that may highlight further commands executed. After triaging, work
  to contain the threat and patch the system that is vulnerable.
data_source:
- Sysmon Event ID 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