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Detection rules › Sigma

Microsoft Excel Add-In Loaded

Status
test
Severity
low
Log source
product windows, category image_load
Author
Nasreddine Bencherchali (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects Microsoft Excel loading an Add-In (.xll) file

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1204.002 User Execution: Malicious File

Event coverage

ProviderEventTitle
SysmonEvent ID 7Image loaded

Rule body yaml

title: Microsoft Excel Add-In Loaded
id: c5f4b5cb-4c25-4249-ba91-aa03626e3185
status: test
description: Detects Microsoft Excel loading an Add-In (.xll) file
references:
    - https://www.mandiant.com/resources/blog/lnk-between-browsers
author: Nasreddine Bencherchali (Nextron Systems)
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

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith: '\excel.exe'
    ImageLoaded|endswith: '.xll'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Imageends_with
  • \excel.exe corpus 18 (sigma 18)
ImageLoadedends_with
  • .xll corpus 2 (sigma 2)