Elastic Security Detection Rules

Microsoft Exchange Server UM Spawning Suspicious Processes

Last updated 5 months ago on 2025-03-20
Created 4 years ago on 2021-03-04

About

Identifies suspicious processes being spawned by the Microsoft Exchange Server Unified Messaging (UM) service. This activity has been observed exploiting CVE-2021-26857.
Tags
Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Initial AccessTactic: Lateral MovementData Source: Elastic EndgameUse Case: VulnerabilityData Source: Elastic DefendData Source: Windows Security Event LogsData Source: Microsoft Defender for EndpointData Source: SysmonData Source: SentinelOneData Source: CrowdstrikeLanguage: eql
Severity
medium
Risk Score
47
MITRE ATT&CK™

Initial Access (TA0001)(opens in a new tab or window)

↳ Exploit Public-Facing Application (T1190)(opens in a new tab or window)

Lateral Movement (TA0008)(opens in a new tab or window)

↳ Exploitation of Remote Services (T1210)(opens in a new tab or window)

False Positive Examples
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.
License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
Event Correlation Rule
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
endgame-*logs-crowdstrike.fdr*logs-endpoint.events.process-*logs-m365_defender.event-*logs-sentinel_one_cloud_funnel.*logs-system.security*logs-windows.forwarded*logs-windows.sysmon_operational-*winlogbeat-*
Related Integrations

endpoint(opens in a new tab or window)

windows(opens in a new tab or window)

system(opens in a new tab or window)

m365_defender(opens in a new tab or window)

sentinel_one_cloud_funnel(opens in a new tab or window)

crowdstrike(opens in a new tab or window)

Query
process where host.os.type == "windows" and 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",
          "?:\\Program Files\\Microsoft\\Exchange Server\\Bin\\UMWorkerProcess.exe",
          "D:\\Exchange 2016\\Bin\\UMWorkerProcess.exe",
          "E:\\ExchangeServer\\Bin\\UMWorkerProcess.exe",
          "D:\\Exchange\\Bin\\UMWorkerProcess.exe",
          "D:\\Exchange Server\\Bin\\UMWorkerProcess.exe",
          "E:\\Exchange Server\\V15\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Windows\\System32\\werfault.exe",
          "\\Device\\HarddiskVolume?\\Windows\\System32\\wermgr.exe",
          "\\Device\\HarddiskVolume?\\Program Files\\Microsoft\\Exchange Server\\V??\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Program Files\\Microsoft\\Exchange Server\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange 2016\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\ExchangeServer\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange Server\\Bin\\UMWorkerProcess.exe",
          "\\Device\\HarddiskVolume?\\Exchange Server\\V15\\Bin\\UMWorkerProcess.exe"
    )

Install detection rules in Elastic Security

Detect Microsoft Exchange Server UM Spawning Suspicious Processes in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).