Code Executed Via Office Add-in XLL File

Status: test
Severity: high
Log source: category ps_script, product windows
Author: frack113
Source: github.com/SigmaHQ/sigma

Adversaries may abuse Microsoft Office add-ins to obtain persistence on a compromised system. Office add-ins can be used to add functionality to Office programs

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1137.006` Office Application Startup: Add-ins

Telemetry coverage

Provider	Record / event type
PowerShell	Event ID 4104: Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body

title: Code Executed Via Office Add-in XLL File
id: 36fbec91-fa1b-4d5d-8df1-8d8edcb632ad
status: test
description: |
    Adversaries may abuse Microsoft Office add-ins to obtain persistence on a compromised system.
    Office add-ins can be used to add functionality to Office programs
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1137.006/T1137.006.md
author: frack113
date: 2021-12-28
tags:
    - attack.persistence
    - attack.t1137.006
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains|all:
            - 'new-object '
            - '-ComObject '
            - '.application'
            - '.RegisterXLL'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    ScriptBlockText|contains|all:
        - 'new-object '
        - '-ComObject '
        - '.application'
        - '.RegisterXLL'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ScriptBlockText`	match	`-ComObject` `.RegisterXLL` `.application` `new-object` corpus 2 (sigma 2)	`field:"ScriptBlockText" kind:match`