Microsoft Exchange Worker Spawning Suspicious Processes

Elastic Stack Serverless Security

Identifies suspicious processes being spawned by the Microsoft Exchange Server worker process (w3wp). This activity may indicate exploitation activity or access to an existing web shell backdoor.

Rule type: eql

Rule indices:

• logs-endpoint.events.*
• winlogbeat-*
• 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/2021/03/02/hafnium-targeting-exchange-servers
• https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities
• https://discuss.elastic.co/t/detection-and-response-for-hafnium-activity/266289

Tags:

• Elastic
• Host
• Windows
• Threat Detection
• Initial Access

Version: 101

Rule authors:

• Elastic

Rule license: Elastic License v2

process where event.type == "start" and
  process.parent.name : "w3wp.exe" and process.parent.args : "MSExchange*AppPool" and
  (process.name : ("cmd.exe", "powershell.exe", "pwsh.exe", "powershell_ise.exe") or
  process.pe.original_file_name in ("cmd.exe", "powershell.exe", "pwsh.dll", "powershell_ise.exe"))

Framework: MITRE ATT&CKTM

• 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/