Windows Excel Loads .XLL Add-In Files
Flags excel.exe loading a .XLL add-in module, an execution indicator for potential malicious add-in activity.
FreeReviewedSigma · Low · v5
- 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
ExecutionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule identifies cases where excel.exe loads an add-in module with a .xll extension. Malicious or tampered add-ins can be abused to execute attacker-controlled code within the context of Microsoft Excel. The detection relies on telemetry from image load events capturing the loaded module path and file extension.
Reporting behind it
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No 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-an-xll-add-in-via-excel-exe-image-load-c5f4b5cb
title: Windows Excel Loads .XLL Add-In Files
id: 14e62d9c-8221-498b-bb7c-51999b3c6222
status: test
description: This rule identifies cases where excel.exe loads an add-in module with a .xll extension. Malicious or tampered add-ins can be abused to execute attacker-controlled code within the context of Microsoft Excel. The detection relies on telemetry from image load events capturing the loaded module path and file extension.
references:
- https://www.mandiant.com/resources/blog/lnk-between-browsers
- https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/image_load/image_load_office_excel_xll_load.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2023-05-12
tags:
- attack.execution
- attack.t1204.002
- detection.threat-hunting
logsource:
category: image_load
product: windows
detection:
selection:
Image|endswith: \excel.exe
ImageLoaded|endswith: .xll
condition: selection
falsepositives:
- The rules is only looking for ".xll" loads. So some false positives are expected with legitimate and allowed XLLs
level: low
license: DRL-1.1
related:
- id: c5f4b5cb-4c25-4249-ba91-aa03626e3185
type: derived