Windows Excel Loads .XLL Add-in from Uncommon File Paths

Flags Excel loading .xll add-ins from uncommon directories based on image load paths.

FreeReviewedSigma · Medium · v2

Product: windows
Category: image_load
Author: Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2023-05-12
Updated: 2026-07-31

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1204.002Malicious File
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule identifies Microsoft Excel (excel.exe) loading an Excel add-in (.xll) from paths that are not typically expected, based on a defined set of uncommon locations. Loading add-ins from unusual directories can help attackers execute malicious code or stage payloads through trusted Office components. The detection relies on image load telemetry showing the excel.exe process and the ImageLoaded path and file extension.

Reporting behind it

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Windows Excel Loads .XLL Add-in from Uncommon File Paths

Pivot detection · T1204.002 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-excel-loads-xll-add-in-from-uncommon-path-af4c4609

title: Windows Excel Loads .XLL Add-in from Uncommon File Paths
id: 7a67a622-3b0f-46ad-8f2d-e533ba74025d
related:
  - id: c5f4b5cb-4c25-4249-ba91-aa03626e3185
    type: derived
  - id: af4c4609-5755-42fe-8075-4effb49f5d44
    type: derived
status: test
description: This rule identifies Microsoft Excel (excel.exe) loading an Excel add-in (.xll) from paths that are not typically expected, based on a defined set of uncommon locations. Loading add-ins from unusual directories can help attackers execute malicious code or stage payloads through trusted Office components. The detection relies on image load telemetry showing the excel.exe process and the ImageLoaded path and file extension.
references:
  - https://www.mandiant.com/resources/blog/lnk-between-browsers
  - https://wazuh.com/blog/detecting-xll-files-used-for-dropping-fin7-jssloader-with-wazuh/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_office_excel_xll_susp_load.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-05-12
tags:
  - attack.execution
  - attack.t1204.002
logsource:
  category: image_load
  product: windows
detection:
  selection:
    Image|endswith: \excel.exe
    ImageLoaded|contains:
      - \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
license: DRL-1.1

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