IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

« Microsoft Build Engine Using an Alternate Name Microsoft Exchange Server UM Writing Suspicious Files »

› › ›

Microsoft Exchange Server UM Spawning Suspicious Processes

edit

Microsoft Exchange Server UM Spawning Suspicious Processes

edit

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: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Elastic
Host
Windows
Threat Detection
Initial Access

Version: 100 (version history)

Added (Elastic Stack release): 7.12.0

Last modified (Elastic Stack release): 8.5.0

Rule authors: Elastic, Austin Songer

Rule license: Elastic License v2

Potential false positives

edit

Legitimate processes may be spawned from the Microsoft Exchange Server Unified Messaging (UM) service. If known processes are causing false positives, they can be exempted from the rule.

Investigation guide

edit

Rule query

edit

process where event.type == "start" and process.parent.name :
("UMService.exe", "UMWorkerProcess.exe") and not
process.executable :
("?:\\Windows\\System32\\werfault.exe",
"?:\\Windows\\System32\\wermgr.exe", "?:\\Program
Files\\Microsoft\\Exchange Server\\V??\\Bin\\UMWorkerProcess.exe",
"D:\\Exchange 2016\\Bin\\UMWorkerProcess.exe",
"E:\\ExchangeServer\\Bin\\UMWorkerProcess.exe")

Threat mapping

edit

Framework: MITRE ATT&CK^TM

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/

Rule version history

edit

Version 100 (8.5.0 release)

Formatting only

Version 4 (8.4.0 release)

Updated query, changed from:

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

Version 2 (8.2.0 release)

Formatting only

« Microsoft Build Engine Using an Alternate Name Microsoft Exchange Server UM Writing Suspicious Files »