Serpent Backdoor Payload Execution Via Scheduled Task

SIGMA detection rule by @kostastsale · NOASSERTION

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.

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

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

7fa1eb61-c3fe-4a45-a4b7-11e8d4aab67a

Propose edits, view related rules, and engage with the community through comments.

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.

Rejected pattern present

[[ reason ]]

What does this mean?

Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

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

[[ currentRule.title ]]

Community Discussion