name: W3WP Spawning Shell
id: 0f03423c-7c6a-11eb-bc47-acde48001122
version: 2
date: '2021-03-03'
author: Michael Haag, Splunk
type: TTP
datamodel:
- Endpoint
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.
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: To successfully implement this search you need to be ingesting information
  on process that include the name of the process responsible for the changes from
  your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition,
  confirm the latest CIM App 4.20 or higher is installed and the latest TA for the
  endpoint product.
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:
  - Hermetic Wiper
  - HAFNIUM Group
  - ProxyShell
  - CISA AA22-257A
  - ProxyNotShell
  - CISA AA22-264A
  confidence: 80
  context:
  - Source:Endpoint
  - Stage:Initial Access
  - Stage:Execution
  cve:
  - CVE-2021-34473
  - CVE-2021-34523
  - CVE-2021-31207
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1505.003/windows-sysmon.log
  impact: 70
  kill_chain_phases:
  - Exploitation
  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
  supported_tas:
  - Splunk_TA_microsoft_sysmon
  asset_type: Endpoint