Microsoft Excel Add-In Loaded From Uncommon Location — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2023-05-12 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 8f40a6c1ebb47898df2449cde054e97b9d040e351d69a2207f1823b5072f1806

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: Microsoft Excel Add-In Loaded From Uncommon Location
id: af4c4609-5755-42fe-8075-4effb49f5d44
related:
    - id: c5f4b5cb-4c25-4249-ba91-aa03626e3185
      type: derived
status: test
description: Detects Microsoft Excel loading an Add-In (.xll) file from an uncommon location
references:
    - https://www.mandiant.com/resources/blog/lnk-between-browsers
    - https://wazuh.com/blog/detecting-xll-files-used-for-dropping-fin7-jssloader-with-wazuh/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-05-12
tags:
    - attack.execution
    - attack.t1204.002
logsource:
    category: image_load
    product: windows
detection:
    selection:
        Image|endswith: '\excel.exe'
        ImageLoaded|contains:
            # Note: Add or remove locations from this list based on your internal policy
            - '\Desktop\'
            - '\Downloads\'
            - '\Perflogs\'
            - '\Temp\'
            - '\Users\Public\'
            - '\Windows\Tasks\'
        ImageLoaded|endswith: '.xll'
    condition: selection
falsepositives:
    - Some tuning might be required to allow or remove certain locations used by the rule if you consider them as safe locations
level: medium

Original YAML and metadata in JSON

False positives

• Some tuning might be required to allow or remove certain locations used by the rule if you consider them as safe locations

Source references

• https://www.mandiant.com/resources/blog/lnk-between-browsers
• https://wazuh.com/blog/detecting-xll-files-used-for-dropping-fin7-jssloader-with-wazuh/