Excel Proxy Executing Regsvr32 With Payload

SIGMA detection rule by Vadim Khrykov (ThreatIntel), Cyb3rEng (Rule) · GPL-2.0

Excel called wmic to finally proxy execute regsvr32 with the payload. An attacker wanted to break suspicious parent-child chain (Office app spawns LOLBin). But we have command-line in the event which allow us to "restore" this suspicious parent-child chain and detect it. Monitor process creation with "wmic process call create" and LOLBins in command-line with parent Office application processes.

title: Excel Proxy Executing Regsvr32 With Payload
id: 72d5e2d6-b55d-f6aa-2db3-4a5fd0d1dd98
related:
    - id: 9d1c72f5-43f0-4da5-9320-648cf2099dd0
      type: derived
status: deprecated
description: |
    Excel called wmic to finally proxy execute regsvr32 with the payload.
    An attacker wanted to break suspicious parent-child chain (Office app spawns LOLBin).
    But we have command-line in the event which allow us to "restore" this suspicious parent-child chain and detect it.
    Monitor process creation with "wmic process call create" and LOLBins in command-line with parent Office application processes.
references:
    - https://thedfirreport.com/2021/03/29/sodinokibi-aka-revil-ransomware/
    - https://github.com/vadim-hunter/Detection-Ideas-Rules/blob/02bcbfc2bfb8b4da601bb30de0344ae453aa1afe/Threat%20Intelligence/The%20DFIR%20Report/20210329_Sodinokibi_(aka_REvil)_Ransomware.yaml
author: Vadim Khrykov (ThreatIntel), Cyb3rEng (Rule)
date: 2021-08-23
modified: 2022-12-02
tags:
    - attack.t1204.002
    - attack.t1047
    - attack.t1218.010
    - attack.execution
    - attack.defense-evasion
logsource:
    product: windows
    category: process_creation
detection:
    process_creation:
        EventID: 4688
        Channel: Security
    selection_img:
        - NewProcessName|endswith: \wbem\WMIC.exe
        - OriginalFileName: wmic.exe
    selection_other:
        CommandLine|contains:
            - regsvr32
            - rundll32
            - msiexec
            - mshta
            - verclsid
        CommandLine|contains|all:
            - process
            - create
            - call
        ParentProcessName|endswith:
            - \winword.exe
            - \excel.exe
            - \powerpnt.exe
    condition: process_creation and (all of selection_*)
falsepositives:
    - Unknown
level: high
ruletype: Sigma

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

1a67b144-42a4-407b-92f6-ce7d2e796604

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

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