Potential Persistence Via Outlook Form

SIGMA detection rule by Tobias Michalski (Nextron Systems) · NOASSERTION

Detects the creation of a new Outlook form which can contain malicious code

title: Potential Persistence Via Outlook Form
id: c3edc6a5-d9d4-48d8-930e-aab518390917
status: test
description: Detects the creation of a new Outlook form which can contain malicious code
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=76
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=79
    - https://learn.microsoft.com/en-us/office/vba/outlook/concepts/outlook-forms/create-an-outlook-form
    - https://www.slipstick.com/developer/custom-form/clean-outlooks-forms-cache/
author: Tobias Michalski (Nextron Systems)
date: 2021-06-10
modified: 2023-02-22
tags:
    - attack.persistence
    - attack.t1137.003
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith: '\outlook.exe'
        TargetFilename|contains:
            - '\AppData\Local\Microsoft\FORMS\IPM'
            - '\Local Settings\Application Data\Microsoft\Forms' # Windows XP
    condition: selection
falsepositives:
    - Legitimate use of outlook forms
level: high

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

6aa2bcb4-ee3c-4377-9b55-6177c8755131

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