Serpent Backdoor Payload Execution Via Scheduled Task

Detects post exploitation execution technique of the Serpent backdoor. According to Proofpoint, one of the commands that the backdoor ran was via creating a temporary scheduled task using an unusual method. It creates a fictitious windows event and a trigger in which once the event is created, it executes the payload.

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Detection logic

selection

Image|endswith:
  - \cmd.exe
  - \powershell.exe
CommandLine|contains|all:
  - "[System/EventID="
  - /create
  - /delete
  - /ec
  - /so
  - /tn run

Condition

selection

Raw YAML

title: Serpent Backdoor Payload Execution Via Scheduled Task
id: d5eb7432-fda4-4bba-a37f-ffa74d9ed639
status: test
description: |
    Detects post exploitation execution technique of the Serpent backdoor.
    According to Proofpoint, one of the commands that the backdoor ran was via creating a temporary scheduled task using an unusual method.
    It creates a fictitious windows event and a trigger in which once the event is created, it executes the payload.
references:
    - https://www.proofpoint.com/us/blog/threat-insight/serpent-no-swiping-new-backdoor-targets-french-entities-unique-attack-chain
author: '@kostastsale'
date: 2022-03-21
tags:
    - attack.privilege-escalation
    - attack.execution
    - attack.persistence
    - attack.t1053.005
    - attack.t1059.006
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains|all:
            - '[System/EventID='
            - '/create'
            - '/delete'
            - '/ec'
            - '/so'
            - '/tn run'
    condition: selection
falsepositives:
    - Unlikely
level: high