Potential Persistence Via Custom Protocol Handler — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-05-30 / 2023-05-12.

{
  "category": "registry_set",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 847940f86b266d5c7a8cda9651ae5c083aba227c129b1139d7494b66c2bb8cfc

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Potential Persistence Via Custom Protocol Handler
id: fdbf0b9d-0182-4c43-893b-a1eaab92d085
status: test
description: Detects potential persistence activity via the registering of a new custom protocole handlers. While legitimate applications register protocole handlers often times during installation. And attacker can abuse this by setting a custom handler to be used as a persistence mechanism.
references:
    - https://ladydebug.com/blog/2019/06/21/custom-protocol-handler-cph/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-05-30
modified: 2023-05-12
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|startswith: 'HKCR\'
        Details|startswith: 'URL:'
    filter_main_ms_trusted:
        Details|startswith: 'URL:ms-' # Microsoft Protocols usually start with "ms-"
    filter_main_generic_locations:
        Image|startswith: # Add more folders to avoid FP
            - 'C:\Program Files (x86)'
            - 'C:\Program Files\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
    # Uncomment This section to add specific Protocol Handler names that are know
    # filter_specific:
    #     Details: 'URL:'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Many legitimate applications can register a new custom protocol handler. Additional filters needs to applied according to your environment.
level: medium

Original YAML and metadata in JSON

False positives

• Many legitimate applications can register a new custom protocol handler. Additional filters needs to applied according to your environment.

Source references

• https://ladydebug.com/blog/2019/06/21/custom-protocol-handler-cph/