Webshell Detection: Script Process Child of Common Web Processes

Elastic Stack Serverless Security

Identifies suspicious commands executed via a web server, which may suggest a vulnerability and remote shell access.

Rule type: eql

Rule indices:

• winlogbeat-*
• logs-endpoint.events.*
• logs-windows.*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://www.microsoft.com/security/blog/2020/02/04/ghost-in-the-shell-investigating-web-shell-attacks/

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Persistence

Version: 3

Rule authors:

• Elastic

Rule license: Elastic License v2

Detections should be investigated to identify if the activity corresponds to legitimate activity. As this rule detects post-exploitation process activity, investigations into this should be prioritized.

process where event.type == "start" and
  process.parent.name : ("w3wp.exe", "httpd.exe", "nginx.exe", "php.exe", "php-cgi.exe", "tomcat.exe") and
  process.name : ("cmd.exe", "cscript.exe", "powershell.exe", "pwsh.exe", "powershell_ise.exe", "wmic.exe", "wscript.exe")

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Persistence
  • ID: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Server Software Component
  • ID: T1505
  • Reference URL: https://attack.mitre.org/techniques/T1505/

• Sub-technique:

  • Name: Web Shell
  • ID: T1505.003
  • Reference URL: https://attack.mitre.org/techniques/T1505/003/

• Tactic:

  • Name: Initial Access
  • ID: TA0001
  • Reference URL: https://attack.mitre.org/tactics/TA0001/

• Technique:

  • Name: Exploit Public-Facing Application
  • ID: T1190
  • Reference URL: https://attack.mitre.org/techniques/T1190/