Potential Persistence Via Outlook Today Page — Sigma Rule

Rule metadata and linked tags

Author: Tobias Michalski (Nextron Systems), David Bertho (@dbertho) & Eirik Sveen (@0xSV1), Storebrand. Source status: test; severity: high. Source dates: 2021-06-10 / 2024-08-07.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 85cafd0009317ce720f0dd159b913df9787494bc25c2dc9675136c2b531be1e5

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 Outlook Today Page
id: 487bb375-12ef-41f6-baae-c6a1572b4dd1
related:
    - id: ddd171b5-2cc6-4975-9e78-f0eccd08cc76
      type: similar
status: test
description: |
    Detects potential persistence activity via outlook today page.
    An attacker can set a custom page to execute arbitrary code and link to it via the registry values "URL" and "UserDefinedUrl".
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=74
    - https://trustedsec.com/blog/specula-turning-outlook-into-a-c2-with-one-registry-change
author: Tobias Michalski (Nextron Systems), David Bertho (@dbertho) & Eirik Sveen (@0xSV1), Storebrand
date: 2021-06-10
modified: 2024-08-07
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    product: windows
    category: registry_set
detection:
    selection_main:
        TargetObject|contains|all:
            - 'Software\Microsoft\Office\'
            - '\Outlook\Today\'
    selection_value_stamp:
        TargetObject|endswith: '\Stamp'
        Details: 'DWORD (0x00000001)'
    selection_value_url:
        TargetObject|endswith:
            - '\URL'
            - '\UserDefinedUrl'
    filter_main_office:
        Image|startswith:
            - 'C:\Program Files\Common Files\Microsoft Shared\ClickToRun\'
            - 'C:\Program Files\Common Files\Microsoft Shared\ClickToRun\Updates\'
        Image|endswith: '\OfficeClickToRun.exe'
    condition: selection_main and 1 of selection_value_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=74
• https://trustedsec.com/blog/specula-turning-outlook-into-a-c2-with-one-registry-change