Detection rules › Sigma
WMI Backdoor Exchange Transport Agent
Detects a WMI backdoor in Exchange Transport Agents via WMI event filters
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | |
| Privilege Escalation |
Telemetry coverage
| Provider | Record / event type |
|---|---|
| Sysmon | Event ID 1: Process creation |
| Security-Auditing | Event ID 4688: A new process has been created. |
Rule body
title: WMI Backdoor Exchange Transport Agent
id: 797011dc-44f4-4e6f-9f10-a8ceefbe566b
status: test
description: Detects a WMI backdoor in Exchange Transport Agents via WMI event filters
references:
- https://twitter.com/cglyer/status/1182389676876980224
- https://twitter.com/cglyer/status/1182391019633029120
author: Florian Roth (Nextron Systems)
date: 2019-10-11
modified: 2023-02-08
tags:
- attack.privilege-escalation
- attack.persistence
- attack.t1546.003
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage|endswith: '\EdgeTransport.exe'
filter_conhost:
Image: 'C:\Windows\System32\conhost.exe'
filter_oleconverter: # FP also documented in https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=18
Image|startswith: 'C:\Program Files\Microsoft\Exchange Server\'
Image|endswith: '\Bin\OleConverter.exe'
condition: selection and not 1 of filter_*
falsepositives:
- Unknown
level: critical
Stages and Predicates
Stage 0: condition
selection and not 1 of filter_*Stage 1: selection
selection:
ParentImage|endswith: '\EdgeTransport.exe'
Stage 2: not filter_*
filter_conhost:
Image: 'C:\Windows\System32\conhost.exe'
filter_oleconverter:
Image|startswith: 'C:\Program Files\Microsoft\Exchange Server\'
Image|endswith: '\Bin\OleConverter.exe'
Exclusions
The rule actively suppresses these predicates.
| Field | Kind | Excluded values | Search |
|---|---|---|---|
Image | ends_with | \Bin\OleConverter.exe | excludes:Image field:"Image" value:"\Bin\OleConverter.exe" |
Image | starts_with | C:\Program Files\Microsoft\Exchange Server\ | excludes:Image field:"Image" value:"C:\Program Files\Microsoft\Exchange Server\" |
Image | eq | C:\Windows\System32\conhost.exe | excludes:Image field:"Image" value:"C:\Windows\System32\conhost.exe" |
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
ParentImage | ends_with |
| field:"ParentImage" kind:ends_with value:"\EdgeTransport.exe" |