Microsoft Exchange Server UM Spawning Suspicious Processes
editMicrosoft Exchange Server UM Spawning Suspicious Processes
editIdentifies 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: 2 (version history)
Added (Elastic Stack release): 7.12.0
Last modified (Elastic Stack release): 8.2.0
Rule authors: Elastic, Austin Songer
Rule license: Elastic License v2
Potential false positives
editLegitimate 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## Config 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.
Rule query
editprocess where event.type == "start" and process.parent.name :
("UMService.exe", "UMWorkerProcess.exe") and not process.name :
("werfault.exe", "wermgr.exe")
Threat mapping
editFramework: 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/
Rule version history
edit- Version 2 (8.2.0 release)
-
- Formatting only