SigmaHQ/rules/windows/file_event/sysmon_cve_2021_26858_msexchange.yml

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title: CVE-2021-26858 Exchange Exploitation
id: b06335b3-55ac-4b41-937e-16b7f5d57dfd
description: Detects possible successful exploitation for vulnerability described in CVE-2021-26858 by looking for |
creation of non-standard files on disk by Exchange Servers Unified Messaging service |
which could indicate dropping web shells or other malicious content
author: Bhabesh Raj
status: experimental
level: critical
references:
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-26858
- https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
date: 2021/03/03
tags:
- attack.t1203
- attack.execution
- cve.2021-26858
logsource:
category: file_event
product: windows
detection:
selection:
Image|endswith: 'UMWorkerProcess.exe'
filter:
TargetFilename|endswith:
- 'CacheCleanup.bin'
- '.txt'
- '.LOG'
- '.cfg'
- 'cleanup.bin'
condition: selection and not filter
fields:
- ComputerName
- TargetFileName
falsepositives:
- Unknown