name: W3WP Spawning Shell
id: 0f03423c-7c6a-11eb-bc47-acde48001122
version: 2
date: '2021-03-03'
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:
  selection1:
    ParentImage: w3wp.exe
  selection2:
    OriginalFileName: Cmd.Exe
  selection3:
    Image|endswith: cmd.exe
  selection4:
    OriginalFileName: Cmd.Exe
  selection5:
    Image|endswith: cmd.exe
  condition: selection1 and selection2 and selection3 or selection4 or selection5
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
  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
  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