Microsoft Exchange Server UM Spawning Suspicious Processes

Elastic Stack Serverless Security

Identifies suspicious processes being spawned by the Microsoft Exchange Server Unified Messaging (UM) service. This activity has been observed exploiting CVE-2021-26857.

Rule type: eql

Rule indices:

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

Severity: medium

Risk score: 47

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

Tags:

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

Version: 2

Rule authors:

• Elastic
• Austin Songer

Rule license: Elastic License v2

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate event.ingested to @timestamp for this rule to work.

process where event.type == "start" and
  process.parent.name : ("UMService.exe", "UMWorkerProcess.exe") and
    not process.name : ("werfault.exe", "wermgr.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/